Media servowriting system

ABSTRACT

A system and methods for efficiently performing media writing functions is disclosed. The system and methods include: detecting media movement with respect to a base and heads during reading and writing, and moving the heads in response; using an interferometer, such as a dual beam differential interferometer, to dynamically monitor disk position and address perceived errors; and minimizing repeatable and non repeatable runout error by writing data, such as servo bursts, in multiple revolutions to average adverse runout conditions. The present system has the ability to use an interferometer to enhance media certification and perform on line, in situ monitoring of the media, and includes shrouding, head mounting, disk biasing, and related mechanical aspects beneficial to media writing.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/367,046, filed Mar. 23, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of data storagemedia, and more specifically to systems and methods for efficientlyinitializing, certifying or otherwise reading data from or writing datato such media.

2. Description of the Related Art

Disk drives are magnetic recording devices used for the storage ofdigital information. The digital information is recorded onsubstantially-concentric tracks on either surface of one or moremagnetic recording disks. The disks are rotatably mounted on a spindlemotor, and information is accessed by read/write heads mounted toactuator arms rotated by a voice coil motor. The voice coil motorrotates the pivoting arms and moves the heads radially over the surfaceof the disk or disks. During servowriting and/or initialization of adisk, the read/write heads must generally be accurately positioned onthe disk to ensure proper reading and writing of servo information thatwill define the data storage tracks. After the servo writer writes theservo patterns on the disks, the control system is added to the harddrive assembly.

Movement of the pivoting arms is controlled by a servo system, whichutilizes servo information recorded on one or more of the disks tocenter the head on a particular track. Servo information is utilized todetermine an actual position of the heads. A voice coil motor (VCM)moves the heads if the actual head position deviates from a desired headlocation. Head position is typically controlled by a closed loop servosystem.

The servo information in the servo tracks is often written with timingderived from a master clock track in the servo writing system. Writingof servo information must be precise. Servo information is typicallyrecorded by special instruments containing precise mechanicalpositioners, positioned using highly accurate feedback devices such asoptical encoders or laser interferometers.

A media servowriter is a device dedicated primarily to the servo datawriting function. It can also perform other functions related to harddisk preparation for insertion into a hard disk drive. In operation, amedia servowriter writes multiple disks in preparation for theirplacement in an HDD, with the goal being minimal further diskpreparation once each disk is located in the HDD. Media servowriters canthus be housed in one location while hard disk assembly includingcompleted disks may be performed at another location with the knowledgethat the servowritten disks have been tested and approved for certainparameters.

Previously available servowriters suffer from a variety of shortcomingsand system performance issues. An example of known system performanceissues is that of system positioning accuracy: positioning heads overtracks to accurately read and write information at high speeds is anongoing performance consideration that can always be improved orenhanced. Most, if not all, of the previously available systems sufferfrom an inability to support custom read/write heads, or provideaccurate micro-move and settle times or track holding accuracy.

One particular problem with currently available disk drives andservowriters is the complexity associated with knowing the location of ahead over a disk, and detecting and utilizing relative movements ofdisks, positioners, heads, and related equipment with respect to areference point or plane. In current servowriters, no action occursduring normal operation to track or control disk or spindle positionwith respect to the drive base. Instead, the system tracks and controlshead position with respect to some servowriter structural referencepoint, with the implicit assumption that disk position is sufficientlywell known and stationary. In actual operation, however, the disks andspindle may shift, vibrate, deform, or otherwise alter their position inspace with respect to the structural reference point. Current systems donot physically track disk position nor compensate for movement orirregularities resulting from real world conditions, including theaforementioned conditions and non-repeatable run out movement. Aservowriter without the ability to track disk position and compensatefor positional or movement irregularities may introduce or otherwisesuffer from errors while heads are reading from or writing to the disks.This error introduction may limit the spin rate and/or track density ofthe disks.

It would be beneficial if one could track and compensate for mediamovement during the read and write process, thereby decreasing the riskof reading from or writing to incorrect locations on the media surface.

Another problem with currently available disk drives and servowriters isthat of accurate head positioning. During the process of writing servotracks on magnetic media, servo patterns must be positioned with highaccuracy on different radial tracks. The traditional method of locatingservo patterns on disks is to use a read/write head flying over aspinning media disk. The read/write head is attached to a rotarypositioning device comprising a voice coil, associated voice coil motor,and a rotary optical encoder for closed loop positioning purposes. Therotary positioning device is used to hold the read/write head and swingthe head over the spinning media disk. Errors in servo track accuracycan occur whenever the system does not maintain head position in acontrolled radius as the media disk spins below the head. In certaincircumstances the axis of the spinning media disk can translatelaterally in the plane of rotation or the axis can wobble, tilting abouta pivot point not coincidence with the media disk plane, thereby alsotranslating the disk with respect to the head. Head position errors mayalso occur if the entire optical encoder fails to precisely track headposition. The entire positioning device can translate or vibrate withrespect to the spinning disk, or flexing of any components connectingthe head to the optical encoder can produce positional errors.

Previous systems have employed a rigid mechanical connection between theoptical encoder and the heads as well as a stable mechanical referencebetween the optical encoder and the axis of the spinning disk. In a diskhaving a track pitch below one micron, the rigid positional linkageperformance between the optical encoder and the head as well as theoptical encoder and spindle axis can be compromised by various factors,such as wobble or translation of the spindle axis within its bearingmount, causing radial runout. Other potentially problematic factors mayinclude tiny distortions of the shape of any hardware that mechanicallyreferences the head to the spindle axis. External vibrations, vibrationsfrom the spindle motor, temperature fluctuations or flutter from thedisk can all contribute nanometer fluctuations and errors in positioningthe head at constant track radius.

It would be beneficial to have a servo system that minimizes thedependence on the idealized mechanical references connecting spindleaxis position to head position, thereby minimizing errors andfluctuations in the radius of servo data, or marks.

Another example of known system performance issues is that of systempositioning accuracy: positioning heads over tracks to accurately readand write information at high speeds is an ongoing performanceconsideration that can always be improved or enhanced. One particularproblem with currently available servowriters is the equipment used toformat a disk writes a set of servo sectors to the disk, and thepresence of relatively significant servo sector errors can cause theservowriter to indicate the disk is bad during verification testing.Alternately, when writing to a formatted disk, the presence ofrelatively significant errors in the servo sectors causes the disk driveto mark those sectors as unusable for data storage, either by detectingexcessive servo errors while track following or excessive errorsdetected during data writing and reading, with the result that the datastorage capacity of the disk would be reduced. Thus the downside of theold method of writing servo sectors or data sectors and monitoring thewritten data for errors would be discarded disks or unusable disk area.These drawbacks decrease yield and reduce available storage capacity.

It would be beneficial to have a method of writing data, including servodata, that would reduce the risk of decreased yields and/or storagecapacity of hard disks as compared with previously known systems.

Furthermore, most, if not all, of the previously available systemssuffer from an inability to support custom read/write heads, or provideaccurate micro-move and settle times or track holding accuracy.

Disk drive heads are replaced periodically due to wear and tear. Insteadof staking, wherein the head suspension and the head mount tab 3501 maysuffer permanent deformation, it would be beneficial to offer a designthat does not encounter permanent mechanical deformation during assemblyor reassembly. In a particular hardware implementation, staking hasrequired mounting a tab replacement or head arm or E-block after onlytwo or three head replacements due to permanent deformation of the bossreceiving bore of the head mount. It would be preferable to offer adesign that can impart less distortion to the interface between the HGAand the mating head mount bore, increasing the number of reuses of thehead mount tab before replacement is indicated.

Further, hard disk drives rely heavily on position reference information“written” or recorded as concentric bands of tracks onto disk surfaces.The operation of creating those tracks, known as servo track writing,requires precise record-phase head positioning and spindle mechanisms,as well as accurate timing and control electronics. The servo trackwriting process traditionally has been performed after disks have beeninstalled into a “hard disk assembly”, or HDA. At the stage where disksare located in an HDA, the disks have been positioned on a spindlewithin the HDA. The HDA read-write heads have been loaded onto the diskor disks. An operator has traditionally placed the HDA onto a ServoTrack Writer device that provides head positioning and servo patterninformation to the HDA to enable proper recording of the servo tracksonto the disk or disks. This traditional technique is especially usefulwhen multiple disks are used within the HDA.

However, as disk areal data density has increased, many Hard Disk Drivestoday utilize only one disk, decreasing the usefulness of theaforementioned technique. Further, increased areal data density isfrequently accompanied by an increase in track density, which requiresthat the HDA write additional servo tracks. With at least two servotracks for every data track, the number of servo tracks has increased attwice the rate of data tracks for a disk of fixed size or area. Thisincreased number of tracks results in a dramatic increase in the timerequired to write the servo tracks. Servo writing, which previously tooka few minutes can now easily exceed a half hour or more, depending onSTW machine parameters, disk size, rotational speed (RPM), and totalnumber of servo tracks. This time increase, coupled with the fact thatmany disk drives today use only a single disk, has created a demand fora media track writer, or MTW, that can simultaneously record servotracks on multiple disks prior to installation into an HDA.

One aspect of the MTW that is particularly noteworthy is the mechanicalclearance between the disk inside diameter, and the hub or chuck outsidediameter, namely the disk opening and the hub that fills the opening. Asignificant clearance dimension is necessary to enable fast and reliabledisk installation on and off the hub and to accommodate disk and hubmanufacturing tolerances. If this clearance is too large, the disk ordisks will move laterally and possibly axially during high RPM rotation.A finite clearance value exists under any set of dimensions. Thisclearance, if not addressed in some manner, creates an uncertainty withregard to the concentricity of servo tracks to disk ID, and can incertain circumstances result in significant eccentricity errorsintroduced when removing disks from the MTW and installed into a diskdrive HAD. If uncontrolled, these errors can in certain circumstancesexceed 4000 microinches, or millionths of an inch. Excessiveeccentricity, or servo track “runout”, can cause servo capture andperformance problems for the HDD, in that the head can be mislocatedabove the disk and can run outside a track, or begin in one track andend in another.

An additional aspect of a media servowriter is holding a hub,specifically a hub of a disk stacking cylinder employed to hold multipledisks during disk servowriting and certification. Previously availablehub holding devices used some type of mechanical “jaws” that gripped theexterior of the hub and/or the notch formed between the hub and the maincylinder. The jaws were formed of some type of metal and were metalpieces used to pin the hub down and hold it in position by applyingpressure to the upper side of the hub. These jaw-type locking devicestend to be imprecise in holding the hub or other cylindrical piece. Atsignificantly high RPMs, such as in excess of 10,000 to 20,000 RPMs,centrifugal force works to pry these devices open, and many jaw typedevices are pried open or move the piece as a result of high forcesapplied thereto. This prying tends to damage the hub and/or maintainingdevice and is generally unacceptable. Thus the previous devices could becharacterized as easily pried open, with poor repeatability, and highlysubject to movement of the piece.

It would be beneficial to provide a system overcoming these drawbackspresent in previously known systems and provide an improved mediaservowriter, disk writer, and/or other device having improvedfunctionality over devices exhibiting those negative aspects describedherein.

SUMMARY OF THE INVENTION

According to one aspect of the present design, there is provided amethod for tracking and controlling media read/write characteristics.The method comprises creating media having a predetermined expectedbaseline configuration, reading the media having the predeterminedexpected baseline configuration, determining whether the media has movedfrom an expected position based on the media reading of thepredetermined expected baseline condition, and correcting data hardwarebased on determining whether the media has moved from the expectedposition.

According to a second aspect of the present design, there is provided amethod for minimizing likelihood of a head within a servowritingapparatus contacting a disk located therein. The method comprisessensing sound intensity in a predetermined frequency range from a firstsensor positioned at a first location within the servowriting apparatus,determining the existence of a pending head crash based on the soundintensity; and moving an element of the servowriting apparatus upondetermining the existence of the pending head crash.

According to a third aspect of the present design, there is provided anapparatus for controlling airflow over rotating media. The apparatuscomprises at least one baffle covering the media, the at least onebaffle comprising at least one cavity shielding at least a portion ofthe rotating media; wherein the at least one baffle provides the abilityto inhibit turbulent flow when the rotating media rotates.

According to a fourth aspect of the present design, there is provided amethod for changing a head assembly employed in a media writing device.The method comprises providing a head mount assembly having a borepassing therethrough, positioning the head assembly adjacent the headmount, aligning the head assembly with the head mount, and press fittingthe head assembly to the head mount.

According to a fifth aspect of the present design, there is provided asystem for detecting movement of a plurality of disks mounted to aspindle. The system comprises a transmitter/receiver capable of emittinga first beam of energy toward the spindle and receiving energy from thespindle and an error calculator determining differences between actualhead position based on the reflective element position and orientationof the spindle.

According to a sixth aspect of the present design, there is provided asystem for positioning a head over a disk, the disk mounted to aspindle. The system comprises a transmitter/receiver capable of emittinga first beam of energy toward the spindle and receiving energy from thespindle, a reflective element positionally emulating the head andoriented to receive a second beam of light energy from thetransmitter/receiver and reflect the second beam back toward thetransmitter/receiver, and an error calculator determining differencesbetween actual head position based on the reflective element positionand orientation of the spindle.

According to a seventh aspect of the present design, there is provided asystem for accurately positioning a head over rotating media, therotating media able to spin about a center axis. The system comprises aninterferometer having the ability to emit light energy and measure aneffective distance between the head and the spindle, and means forcomputing a correction factor to be applied to the spindle to correctfor any perceived distance errors related to the head measurement.

According to an eighth aspect of the present design, there is provided asystem for determining spindle orientation inaccuracies. The systemcomprises an interferometer having the ability to emit light energy andmeasure an effective distance between the interferometer and thespindle, and means for computing a correction factor for application tothe spindle to correct for perceived errors.

According to a ninth aspect of the present design, there is provided amethod for increasing magnetic disk yield during the manufacturingprocess. The method comprises initially writing a first complete set ofservo data to a magnetic disk, subsequently writing at least oneadditional set of servo data to the magnetic disk, evaluating thequality of the servo data written, and removing the lowest quality servodata and retaining the highest quality servo data.

According to a tenth aspect of the present design, there is provided amethod of assessing track writing performance on a media. The methodcomprises monitoring spindle axis position with respect to a referenceposition, and providing the spindle axis position with respect to areference position to a processor.

According to an eleventh aspect of the present design, there is provideda method of computing a media track writing performance metric. Themethod comprises at least one from the group including computing astandard deviation of an observed track write radius from a desiredtrack write radius and decomposing the standard deviation intorepeatable and nonrepeatable components, computing time dependent servomark positions, and computing optically inferred spindle axis positions.

According to a twelfth aspect of the present design, there is provided amethod of computing a performance metric for media track writing. Themethod comprises monitoring position of a rotating component of a holdermaintaining the media, computing a topological radius of a surface ofthe rotating component, and determining a difference between therotating component position and the topological radius, wherein thedifference equals rotating component wobble.

According to a thirteenth aspect of the present design, there isprovided a method for biasing at least one disk fixedly attached to aspindle. The method comprises applying a biasing lateral force to afirst disk fixedly attached to the spindle thereby tightly interfacingthe disk with the spindle at one portion of the disk and applying adifferently oriented biasing lateral force to any second disk fixedlyattached to the spindle.

According to a fourteenth aspect of the present design, there isprovided a method for biasing a disk attached to a spindle, comprisingapplying a biasing lateral force to the disk fixedly attached to thespindle thereby tightly interfacing the disk with the spindle at oneportion of the disk.

According to a fifteenth aspect of the present design, there is provideda system for maintaining media, comprising a cap, at least one springholding the cap, and a fluid release ball bearing arrangement having theability to slidably engage and release the cap using force generated bythe at least one spring.

According to a sixteenth aspect of the present design, there is provideda device for holding a rotating hub, comprising a chuck clamp housing, amounting plate fixedly mounted to the chuck clamp housing, a spindlewithin the chuck mounting plate, and a chuck clamp surrounding the chuckmounting plate and having the ability to engage the hub, wherein thechuck clamp comprises a plurality of finger elements.

These and other objects and advantages of the present invention willbecome apparent to those skilled in the art from the following detaileddescription of the invention and the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general conceptual representation of the servowriting systemaccording to one aspect of the current invention;

FIG. 2 represents the mechanics of the servo writing device of oneaspect of the current invention;

FIG. 3 is the multiple disk and spindle arrangement used in accordancewith one aspect of the current invention;

FIG. 4 presents a single multiple read/write head positioner arrangementthat may be utilized in accordance with one aspect of the currentinvention;

FIG. 5 presents an alternate view of the servowriting device with mediacover and in-place positioner according to one aspect of the currentinvention;

FIG. 6 is a conceptual view of the optical inspection system accordingto one aspect of the current invention;

FIG. 7 shows ideal operation of writing bursts to a track;

FIG. 8 illustrates a more typical operation of burst writing observedunder certain typical conditions;

FIG. 9 shows a conceptual illustration of the sinusoidal dipulse writingof a burst;

FIG. 10 presents multiple dipulse writing over multiple passes inaccordance with an aspect of the present invention;

FIG. 11 represents one aspect of the inventive device disclosed herein;

FIG. 12 represents the relationship between a single data sector and anassociated servo sector;

FIG. 13 shows the disposition of servo sectors at substantially regularangular offset positions around the disk according to one aspect of thecurrent invention;

FIG. 14 is a schematic cross-sectional view at some point along thelength of a fiber optical tri-coupler such as used in an interferometeraccording to one aspect of the current invention;

FIG. 15 is a schematic of an embodiment of an interferometer accordingto the present invention;

FIG. 16 is a schematic of an alternate embodiment of an interferometeraccording to the present invention;

FIG. 17 is a graph showing the output signals from photodetectors on theinterferometer versus the input phase-difference between the input beamsaccording to one aspect of the current invention;

FIG. 18 represents a conceptual top view of an acoustic sensorimplemented in one aspect of the present invention;

FIG. 19 illustrates a perspective view of the left baffle shroudaccording to one aspect of the present invention;

FIG. 20 is a perspective view of an eleven-shroud right baffle accordingto one aspect of the present invention;

FIG. 21 represents the hardware associated with the servo writing deviceaccording to one aspect of the current invention;

FIG. 22 is a top cutaway view of the left baffle shroud according to oneaspect of the current invention;

FIG. 23 presents a side cutaway view of the left baffle shroud accordingto one aspect of the current invention;

FIG. 24 shows a bottom view of the left baffle shroud according to oneaspect of the current invention;

FIG. 25 illustrates a side view of the right baffle shroud according toone aspect of the current invention;

FIG. 26 is an alternate perspective view of the right baffle shroudaccording to one aspect of the current invention;

FIG. 27 shows a bottom view of the right baffle shroud according to oneaspect of the current invention;

FIG. 28 is a perspective view of the clock shroud according to anotheraspect of the current invention;

FIG. 29 presents a top view of the clock shroud of FIG. 28 according toone aspect of the current invention;

FIG. 30 is a rotary voice coil motor design according to one embodimentof the current invention;

FIG. 31 presents a coil housing according to one embodiment of thecurrent invention;

FIG. 32 presents a front and side view of a coil according to oneembodiment of the current invention;

FIG. 33 shows a scale holder and shaft used to maintain and rotate thepositioner, E-block, and related components according to one embodimentof the current invention;

FIG. 34 shows the E-block assembly, including a plurality of headsattached thereto on head assemblies according to one embodiment of thecurrent invention;

FIG. 35 shows an example of a mounting tab that may be mounted to theE-block and that may operate in accordance with the present inventionaccording to one embodiment of the current invention;

FIG. 36 shows a top view of the E-Block bifurcated by a centerline andparticularly highlighting the slots for receiving the dowels or pins ofthe mounting tab according to one embodiment of the current invention;

FIG. 37 is an exploded view of one aspect of an assembly tool that maybe used in accordance with the present invention;

FIG. 38A shows front and side views of one aspect of a left section ofan assembly tool according to one embodiment of the current invention;

FIG. 38B illustrates front, rear, and side views of one aspect of acenter section of an assembly tool according to one embodiment of thecurrent invention;

FIG. 38C represents front and side views of one aspect of a rightsection of an assembly tool according to one embodiment of the currentinvention;

FIG. 39 shows various components that may be employed in the inventivepress fit method disclosed herein according to one embodiment of thecurrent invention;

FIG. 40 shows one detailed aspect of a head assembly according to oneembodiment of the current invention;

FIG. 41 is a view of an assembly tool maintaining a mounting tab andhead assembly prior to press fitting with an alignment pin insertedtherethrough according to one embodiment of the current invention;

FIG. 42 illustrates an assembly tool maintaining a mounting tab and headassembly prior to press fitting with a second alignment pin insertedtherethrough according to one embodiment of the current invention;

FIG. 43 shows an assembly tool maintaining a mounting tab and headassembly and press fitting the components together using a vise orclamping device according to one embodiment of the current invention;

FIG. 44 is an aspect of the locking cap arrangement of a systemaccording to one aspect of the current invention;

FIG. 45 is a close view of a locking cap according to an aspect of thepresent invention;

FIG. 46 is an aspect of the locking cap arrangement with bearingsreleased and in release position according to one embodiment of thecurrent invention;

FIG. 47 is a close view of the locking cap arrangement with bearingsreleased and in release position according to one embodiment of thecurrent invention;

FIG. 48 illustrates the finger gripping arrangement used to grip a hubholding one or more disks according to one embodiment of the currentinvention;

FIG. 49 is an alternate view of the finger gripping mechanism accordingto one embodiment of the current invention; and

FIG. 50 is another alternate view of the finger gripping mechanismaccording to one embodiment of the current invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, there is provided an enhanced mediaservowriter having several aspects constituting improvements overpreviously known designs. An aspect of the present invention is a systemand method for tracking disk and spindle position, typically in amultiple media disk arrangement, whereby data from the disks or spindleare fed back to hardware and/or software to compensate for positionerrors during reading and/or writing to the media.

In a particular aspect of the present invention, a non-contact radiationdetection system cooperates with an ideal disk produced using patterningtechnology to detect movement of disks mechanically coupled to aspindle. The system further utilizes an ideal magnetic disk to detectmovement of disks mechanically coupled to a spindle. Further, the systemand method disclosed herein detect spindle and disk (or disks) movementwith respect to a common base by detecting radiation reflected by arotating part of the spindle.

A particular implementation measures and calculates the distance betweenthe spindle axis position and an emulated head position and uses thisdistance to more accurately position the head. The system may employ adual channel interferometer, such as a multiphase or guided waveinterferometer, to reflect energy beams off the spindle holding therotating media by using a retro reflector emulating head position and alensing arrangement. The interferometer determines actual distance fromthe head to the spindle using the emulated head position and the systemutilizes a digital signal processor or other computing device to comparethat distance to any topological shift in the spindle position to findan overall error. The system then applies the overall error to the voicecoil to correct head position. Alternate aspects of the invention employinterferometers in the z (vertical) direction or in the y direction todetermine and compensate for tilt, vibration, or other undesirable mediaand/or head shifting.

In one aspect, the interferometer operates by reflecting light off thepolished chuck holding the disks, which is part of the rotating portionof the spindle and thus accurately emulates spindle axis position andorientation. Due to errors in the spindle chuck (not perfectlycylindrical, tilted or otherwise computationally off desiredorientation) the system determines the topological offset of the chuckand uses this value in combination with the raw distance between thehead and the chuck and/or spindle to determine an overall positionalerror rate signal. The DSP processes this error signal to produce acorrective positional signal, which the DSP applies to the voice coil orother control device. The result is a compensation for angular tiltand/or shifts in orientation and/or the relationship between the head orthe media. The retro reflector may be a corner cube or cat's eye or anyother optical element having beneficial functionality in thisinterferometer-emulated head position arrangement.

The devices and methods disclosed herein may be employed in servowritingand/or data writing systems, and may be used in other systems employinga device such as a head to write or read data to or from rotating media.

A further aspect of the present invention includes a method forincreasing the yield of magnetic disks during the manufacturing process.According to an aspect of the present invention, once the system haswritten the set of servo sectors to the disk, the servowriter verifiesdata written in the servo sectors to validate the disk. If the datawritten within the servo sectors exhibits sufficient integrity, theservowriting process is considered successful, and data sectorscorresponding to the servo sectors are produced and validated. The datasectors may store data subsequently written to the disk.

Another aspect of the invention utilizes the writing and readingconcepts disclosed above to increase the data storage capacity of a harddisk drive by writing multiple duplicate versions of data to the disk indifferent data sectors around the disk, and then retaining only the dataexhibiting a sufficient degree of integrity. In this aspect of theinvention, similar to the servowriting aspect outlined above, more thanone set of data sectors is written to the media disk during normaloperation, preferably during the same revolution. As a result, insteadof a single set of data sectors disposed at predetermined positionsaround the disk based on available space on the disk, this aspect of themethod disclosed herein produces one or more additional sets of datasectors, each of these data sectors being disposed at predeterminedpositions around the disk with respect to other data sectors. Oncewritten, the HDD determines the set of data having the highest dataintegrity by comparing all data sets against original or baseline data.The system may then erase lower quality or duplicate data.

A further aspect of the present invention is tracking disk and spindleposition, typically in a multiple media disk arrangement, whereby datafrom the disks or spindle are fed back to hardware and/or software tocompensate for position errors during reading and/or writing to themedia. This aspect of the invention may or may not be used with thehardware disclosed. A non-contact radiation detection system cooperateswith an ideal disk produced using patterning technology to detectmovement of disks mechanically coupled to a spindle. Another aspect ofthe present invention utilizes an ideal magnetic disk to detect movementof disks mechanically coupled to a spindle. An aspect of the inventionprovides a system and method for detecting spindle and disk (or disks)movement with respect to a common base by detecting radiation reflectedby a part of the spindle.

Media Servowriter

FIG. 1 is a general conceptual representation of the servowriting systemin which the present invention may be employed. From FIG. 1, the systemcontroller 102 controls clock pattern 103, robotics control 104,position servo 105, and PES and verify block 106. Robotics control 104,position servo 105, and PES and verify blocked 106 perform functionsrelated to the present invention. For example, robotics control 104provides commands to drive the motors and sensors interacting with thespindle and air bearing to drive the multidisk spindle and air bearingarrangement.

In one embodiment, clock pattern circuit 103 generates a clocking signaland establishes the pattern generated on the disk surface. Systemcontroller 102 provides an indication to clock pattern circuit 103 toinitiate a pattern on the disk surface when appropriate, such as duringdisk processing routines when it is appropriate for certification andservowriting to occur. Pattern read/write block 107 provides signals forreading and writing the pattern established by the clock pattern circuit103. This pattern is the pattern used for this certification asdescribed herein, which is written to and read from the media. Clockpattern circuit 103 also issues commands for servo/clock writing toservo clock read/write circuit 108. Servo clock read/write circuit 109writes servo clock information to the disk and reads that clockinginformation to assess the validity of the servo data.Servo/certification module 110 determines the proper time, data, andpattern for servowriting for the multiple head/multiple disk arrangementof the present invention.

Operation of servo/certification module 110 in one embodiment isdescribed below. Servo certification module 110 receives data frompattern read/write block 107 and servo clock read/write circuit 108.Servo certification module 110 transmits appropriate data and receivesrelevant data at multiple data preamps 111 a through 111 n, where n isthe total number of preamps used to write to multiple disks. Forexample, but without limitation, a system may employ ten disks andtwenty heads in connection with four preamps. Uniform correspondence inpreamp to disk ratio between data preamps is not required, and one datapreamp may write to one disk while another may write to several mediadisks in the same configuration. Multiple data preamp and diskarrangements may be employed while still within the course and scope ofthe present invention. Servo clock read/write circuit 108 also transmitsand receives relevant data at clock preamp 112. These preamps filter andamplify data received from the various circuits and transmit theamplified signals to the appropriate read/write heads 113 a-n.

In association with one possible implementation of the presentinvention, media disks are located on spindle 120 and read/write heads113 a-n positioned proximate the disk surface using the head stackassembly. The spindle 120 preferably rides on an air bearing 122,thereby operating to rotate the disks in an efficient manner whilemultiple heads engage the media 121, such as multiple hard disks 121a-n, in order to read and write appropriate information. The systemwrites patterns, including servo patterns, to each disk using theread/write heads. As reading and writing using multiple heads mayinvolve simultaneous processing, reduced processing requirements andtime sharing could result in significant cost savings. The system writesservo data and performs certification in a timely and cost effectivemanner using the spindle 120 and head stack assembly arrangement.

Compensation for Head and Disk Movement

One aspect of the invention disclosed herein detects movement (otherthan spinning) of the spindle and/or media, such as computer disks, withrespect to a reference location, such as a granite base to which diskdrive or servowriter hardware is attached, or directly with respect to ahead interacting with the media. The present invention comprises methodsand systems for compensating for such movement. The result of thisaspect of the invention is to in most cases decrease the relativemovement (other than spinning) between the heads and disks during normaldisk drive or servowriting operation.

Four aspects and various related embodiments of the current inventionare specifically disclosed herein for detecting movement of media disksand/or the spindle holding the media with respect to the base. Thesefour aspects compensate movement with respect to the base and/or heads.The first aspect is a non-contact radiation detection system combinedwith an ideal disk produced using patterning technology. The secondaspect is an ideal magnetic disk serving as a reference for a headreading information from the ideal magnetic disk. The third aspect is anon-contact radiation detection system that bounces radiation off one ormore parts of the spindle. The fourth aspect is a non-contact radiationdetection system that bounces radiation off both a part of the spindleand one or more parts of one or more heads.

1. Non-Contact Radiation Detection System Combined with an Ideal DiskProduced Using Patterning Technology

In a first aspect of the current invention, a non-contact radiationdetection system cooperates with an ideal disk produced using patterningtechnology to detect movement of disks mechanically coupled to aspindle.

From FIG. 2, the current system comprises a base 201, having a mountingblock (not shown) or other holding device affixed thereto. The mountingblock is fixedly mounted to a spindle 202. The rotating spindle maymaintain a plurality of media disks 204 (a) through (n), illustrated infurther detail in FIG. 3, but may maintain a single disk or virtuallyany number of disks. In the configuration shown, ten disks are employedand are secured by locking cap 302 and chuck clamp 303. Positioner 401of FIG. 4 maintains a series of heads 403(a) through (n), typicallyindividual read/write heads that perform both reading and writingfunctions, where each head flies over the surface of the media 204(a)through (n), which are typically hard disks. A depiction of the entiresystem is presented in FIG. 5, wherein the positioner 401 is closelyassociated with the disk stack and a VCM motor 502 to read from andwrite to the disks.

In the current aspect of the present invention, an ideal disk (notshown) comprising positional guiding information, such as a particulardata and/or servo data track structure, is produced possibly separateand apart from the configuration illustrated in FIG. 3. The ideal diskmay be produced using the FIG. 2 through 5 configuration, but it istypically not produced in the same multi-disk situation as illustratedin FIG. 3.

According to an aspect of the invention, the ideal disk is producedusing patterning technology. In one case, the ideal disk is producedusing lithography methods, as employed in the semiconductor industry. Inanother case, the ideal disk is produced using an electron beam (e.g.,the tracks on the disk are written using an electron beam). This idealdisk is used as a reference for the subsequent media reading and writingfunctions performed by the system of FIG. 1. If the ideal disk is amagnetic disk, the system reads magnetic reference data. If the idealdisk is produced using patterning technology, lithography, or an e-beam,reading reference data from the disk may include employing a device suchas a laser positioning system employing, for example, reflection,refraction, or transmission, such as in the case where physical holesare placed in the ideal disk.

In one embodiment, the ideal disk produced using methods disclosedherein is then mechanically coupled to the spindle along with any otherdisks that may normally be coupled to the spindle. In a particularapplication, a plurality of disks to be written or tested is arranged ina stacked formation and is mechanically coupled to the spindle. In thisparticular application, the ideal disk is also mechanically coupled tothe spindle to detect movement of the spindle, and implicitly, of one ormore of the stacked disks. More than one ideal disk may be attached tothe spindle to further improve the accuracy of the movement detectionprocess. In the present arrangement, the system has predeterminedknowledge of the parameters of the ideal, or reference, disk and usesthe ideal disk to form a reference point for tracking the actualposition of the spindle and media located thereon. Use of additionalideal disks provides further reference points to track and eliminatemedia position irregularities.

A non-contact radiation detection system interacts with the ideal diskto detect movement of the ideal disk, and implicitly, of the spindlemechanically coupled to the ideal disk.

In one aspect of this non-contact radiation detection system, thenon-contact radiation detection system comprises an optical system,conceptually illustrated in FIG. 6. The optical system 601 comprises anoptical transmitter 602, such as a laser diode, and an optical receiver603, such as an optical detector. The optical transmitter and receivermay be disposed on the base of the system, such as at base 201, and maycooperate to detect movement of the ideal disk with respect to the base201. Depending on the structure and properties of the ideal disk, theoptical transmitter and receiver may be disposed on opposite sides ofthe ideal disk. For example, the positional guiding information may bederived from apertures that permit transmission of optical radiation.Alternately, positional guiding information may be derived from a sameside of the ideal disk. For example, the positional guiding informationand/or the ideal disk may exhibit reflective properties, and data may betransmitted to the disk surface and be reflected and interpretedtherefrom.

The optical system 601 detects movement of the ideal disk with respectto the optical transmitter 602 and receiver 603. Hardware and/orsoftware logic utilizes the information provided by the optical systemto determine the magnitude and direction of movement at any point alongthe spindle or on the disks, both with respect to the base and withrespect to any heads operating on the disks. In one aspect, the opticalsystem may be affixed or mechanically interconnected to the base 201,and the optical system 601 knows the position of the base 201, thespindle, and the disks. The optical system monitors disk positionrelative to its own position and transmits any variations to hardwareand/or software logic to correct for perceived deviations based on thepattern observed from the ideal disk. Once the direction and magnitudeof motion of a particular disk is determined at a point proximate to acorresponding head reading from, or writing to the disk, the head movesaccordingly to compensate for disk motion. As a result, the systemminimizes or eliminates relative motion of the head with respect to themedia disk.

In a particular implementation, a voice coil motor (VCM) that normallyengages and operates the head utilizes information provided by theoptical system 601 and/or other logic to move the head in response todisk movement. In this implementation, the head is substantially rigidlycoupled to an arm that moves under control of the VCM. A positionaldifference in the ideal disk perceived by the optical system 201 isprovided to the VCM logic such that the head and arm are moved tocompensate for the perceived positional shift. In many situations, thepositional shift will be a rotation that is too fast or too slow,meaning the head is either ahead of or behind its desired position. Insuch a lead or lag situation, the rotation of the system may be alteredor the head shifted forward or backward in the rotation.

In an alternative implementation, the head is mechanically coupled via ajointed connection to a first end of the arm controlled by the VCM, andthe head may move (rotate or translate) with respect to the first end ofthe arm under the control of one or more actuators.

2. Ideal Magnetic Disk Serving as a Reference for a Head

Another aspect of the present invention utilizes an ideal magnetic diskto detect movement of disks mechanically coupled to a spindle.

An ideal magnetic disk comprising positional guiding information, suchas a preferred data and/or servo-data track structure, is producedaccording to an aspect of the present invention. The ideal magnetic diskmay be produced separate and apart from the multiple disk configurationof FIGS. 2 through 5, but this is not specifically required. The idealmagnetic disk having magnetic positional information located thereon isthen mechanically coupled to the spindle, in addition to any other disksthat may normally be coupled to the spindle. In a particularapplication, a plurality of disks to be written or tested is arranged ina stacked formation and is mechanically coupled to the spindle, as inFIG. 2. In this particular application, the ideal magnetic disk is alsomechanically coupled to the spindle to detect movement of the spindle,and implicitly, of one or more of the stacked disks. More than one idealmagnetic disk may be attached to the spindle to again improve theaccuracy of the movement detection process.

Thus the system may reduce relative movement between the head and theideal disk by either moving the spindle in combination with the disk(s),or moving the heads. If moving the spindle, such movement may beaccomplished using an air pulse, a mechanical centrifugal device such asa screw or actuator, varying the magnetic field in the spindleelectromotor, or varying the external magnetic field surrounding thespindle. If the system reduces relative movement by moving the heads, itemploys either jointed head arms having individual actuators locatedthereon, moving only the tip of the head arm, or alternately may movethe entire head arm.

According to one aspect of the invention, the ideal magnetic disk (notshown) is produced by writing a data or servo track in multiplerevolutions instead of writing the track in a single revolution.Commonly, a data or servo track may be written in a single revolution,but the track may exhibit random deviations from the desirable circularpattern. The random deviations may include non repeatable run out errorsthat may occur due to temporary and nonrecurring factors. An aspect ofthe current invention is to provide for writing such a track duringmultiple revolutions by partitioning the track into multiple segmentsand writing different segments in different revolutions to average outthe random deviations. By writing different segments of the track duringdifferent passes, random errors introduced into the system by sourcesthat move the disks with respect to the heads are averaged out, therebybeing reduced or eliminated.

One aspect of the current invention associated with employing an idealmagnetic disk as a reference is that of writing servo bursts in multiplerevolutions to average the adverse affects associated with servowriting,such as the problem of non-repetitive run out. This aspect requireswriting servo data in multiple revolutions. Under previously knownservowriting operation, when the system servowrites a track, the NRRO(non-repetitive run out) occurring during the servowriting revolution iswritten into the track. The NRRO contribution can be minimized byaveraging such writing over all or part of servowritten data. Datawriting averaging may be achieved by writing a servo burst in multiplerevolutions, with different portions of the servo data written indifferent revolutions.

In a particular implementation of the invention, one or more portions ofthe servo data may be written multiple times in substantially the samephysical location on the disk during different tracks. Writing aparticular portion of servo data more than one time may be desirableunder various circumstances, including, for example, to assesscharacteristics of the disk and/or heads, or to improve the accuracy ofthe track by further averaging out random errors. In a particularembodiment, writing a particular portion of servo data more than onetime may be achieved by partially or fully overlapping data written tocontiguous portions of the disk.

In operation, in one embodiment of the invention, the servowriter writesa long track, such as a four-revolution track, during four separaterevolutions. The segments written every revolution produce the finalservo pattern. In one case, the system performs dynamic control of thewrite gate to avoid overwriting portions written in previousrevolutions, i.e. the write gate does not write when commanded under allconditions as had been done on previous systems. In another case, thesystem performs dynamic control of the write gate but permits partial ortotal overwriting of one or more portions written in previousrevolutions. The switching of head current in connection withembodiments disclosed herein may be performed at a significant rate,typically higher than that previously done. The rate at which the headcurrent is switched may be decreased in situations where the systemwrites data patterns comprising segments spaced further apart on thedisk.

According to this aspect of the invention, the system writes servo datamultiple times over the surface of the disk. For example, servo data fora certain position of the disk may be written more than once, such asfour times, to the same area. Alternatively, a particular segment ofdata may be partitioned into multiple overlapping, contiguous and/ornon-contiguous subsegments, and the subsegments may be written duringone or more different revolutions. In either case, should one of thewriting functions suffer from non-repetitive runout, that writingfunction may be averaged with the other writing functions and the systemmay selectively read from the areas exceeding or not exceeding anaveraged threshold, or a combined threshold. This averaging techniquemay be achieved by writing the servo data multiple times over a singledisk.

FIGS. 7-10 illustrate further aspects of the system relating to theconcept of the averaging technique of an aspect of the invention. FIG. 7shows normal operation of writing bursts to a track. Track 701 is thetarget for writing and also subsequently for reading of informationusing a series of bursts. First burst 702, or Burst A, is written first,and second burst 703, or Burst B, is written thereafter. FIG. 7 is anideal version of the burst writing arrangement. In reality, tracks maybe neither perfectly straight nor perfectly circular, and burst writingis frequently inexact, off center, too short or too long, and/orotherwise imperfect. A more typical illustration is provided in FIG. 8,wherein burst A spans the track and Burst B is located entirely off thetrack. This effect makes reading and writing over the locations asimprecise and undesirable. A conventional write head writes a burst in asingle revolution, shown in FIG. 9 as Burst A 901. In reality, thisconceptual depiction of Burst A 901 may be inaccurate, as the head mayimpart a magnetic signal in the form of a typical sine wave to the trackand disk, such as that shown as magnetic signal 902.

Thus, according to the embodiments of FIGS. 7 and 8, writing of Burst Aand Burst B comprises writing a first set of data in a sine wave asBurst A and a second set of data in a sine wave on the opposite side ofthe track as Burst B. The result may be sine waves disposed in variedorientation on the disk with respect to the track. In one case, once thehead writes Bursts A and B to the disk, the system positions the readand/or write head on the track and reads the A and B Bursts. SA and SBrepresent the energy perceived by reading Bursts A and B, respectively.In a particular implementation, the head passes the received energy forthe two bursts to hardware and/or software to compute the followingenergy value:E=(S _(A) −S _(B))/(S _(A) +S _(B))

If the Burst A and Burst B energy levels are equal, this value goes tozero, indicating that Bursts A and B are located close to theirdesirable positions along the intended track. If the magnitude of energyE exceeds a particular threshold, the system may decide that theposition, shape, or other relevant characteristics of the track areunsatisfactory, and may choose to reposition the head and rewrite BurstsA and B. Correction of such position, shape, or other relevantcharacteristics of the track may be achieved and verified by decreasingthe magnitude of energy E.

Since the value of E may be positive or negative, in one embodiment thesystem may utilize two different thresholds, depending on whether E ispositive or negative. The two thresholds may also be equal in magnitudebut opposite in sign. The thresholds may be predetermined based oncharacteristics of the disk and/or system, or may be dynamicallycomputed and/or adjusted along the tracks based on information that thesystem obtains while writing and reading tracks. The sign of E may beused to assess which of Bursts A or B is deviating more from a desirableposition, and this assessment may be utilized to select an appropriatecorrective action. In one case, the system may select to only rewrite aparticular burst. In other cases, the system may select to rewrite morethan one burst, or a combination of complete and/or partial bursts. Inother embodiments of the invention, other methods may be employed todetermine undesirable deviations in position, shape, or other relevantcharacteristics of the track, including more complex mathematical modelsand formulas for the energy E.

In previous systems, an inaccurately-written track would either gouncorrected or would require reading the written area, erasing badtracks, and again writing the data, but this could again have the datawriting errors such as those pictured in FIG. 8 and/or may waste timeand system resources.

According to one aspect of the present invention, the system writes theA and B bursts in multiple revolutions over the same disk area. FIG. 10illustrates writing a first sinusoidal dipulse 1001 for Burst A at thebeginning of the desired Burst A location, followed by a second dipulse1002 for Burst B at the beginning of the desired Burst B location. On asecond pass, the head writes the second Burst A dipulse 1003 offset inposition from the first Burst A dipulse 1001, possibly at or near theend of the first dipulse 1001 point. Second Burst B dipulse 1004 issimilarly written at a position offset from first Burst B dipulse, andpossibly at or near the completion point of the first Burst B dipulse1002. The system can step through the Burst dipulses and may write morethan one dipulse per pass, illustrated by the ellipsis in FIG. 10. Twopasses may be employed, or more than two passes, within the scope of thepresent invention. Alternatively, the system may write partial dipulsesin various passes, or a combination of partial and full dipulses.

The result of this partial burst writing technique employed on multiplepasses is to provide an averaged positioning and signal strength forburst writing such that writing on a single pass with a single offsetbecomes unlikely. Should one pass suffer from an offset during thewriting procedure, that offset may be corrected or decreased insubsequent passes.

A drive having a substantially-constant offset at all times, or a bias,may be unacceptable and improperly operating. The system may elect tocorrect this bias. Alternatively, such a bias may be detected andcommunicated to a disk drive comprising the respective disk, such thatthe disk drive may utilize the bias to follow the track comprising thebias. In one case, such a bias may be attributed to repeatable run offerrors.

The effect addressed by the present aspect of the system is random noiseor intermittent wandering experienced during writing under normaloperation. Over a number of passes, it is to be understood that thepresent aspect of the system tends to reduce adverse effects due toerrant dipulse and burst writing.

It is to be understood also that part of a dipulse may be written in onepass, or multiple dipulses, but in most cases the entire burst area andall dipulses are not written in a single pass for a particular databurst. Thus it is within the scope of the present system to write asubset of the pulse or a number of dipulses which is less than all ofthe dipulses to the disk in a first pass, then an additional dipulse ornumber of dipulses or portion of the burst or portions of the burst on asubsequent pass or multiple subsequent passes.

Once this multiple pass data burst writing technique is completed, thesystem may optionally compute the energy calculation provided above forBursts A and B. While the energy errors may be less for the disk writtenaccording to the multiple pass technique, should the value of the energycomputation be outside a particular range the bursts may need to berewritten. This reading, energy computation, assessment, and rewritingis optional but may have a tendency to provide enhanced and improvedburst writing capability.

With respect to the magnetic disk aspect of the present system,according to an aspect of the invention, once an ideal magnetic disk isproduced, the ideal magnetic disk is mechanically coupled to thespindle, possibly in addition to other disks to be written or testedstacked thereon, such as in the configuration illustrated in FIG. 1. Theideal magnetic disk spins together with the other disks. Alternatively,the ideal magnetic disk may not spin together with the other disks, butmay be offset by a predetermined, predictable or determinable amountwith respect to the other disks. As previously mentioned, more than oneideal magnetic disk may be utilized.

In one embodiment, a detector head reads information stored on the idealmagnetic disk and detects movement of the ideal magnetic disk withrespect to the head. Hardware and/or software logic utilizes theinformation provided by the detector head to determine the magnitude anddirection of movement at any point along the spindle or on the disks,with respect to any heads operating on the disks. If the disk is aheador behind the point where it should be, for example, the differentialbetween the present position and the desired position is applied tohardware and/or software logic to either alter the spin of the disk oralter the head position to move into closer synchronization with thepreferred position. In other words, once the system determines thedirection and magnitude of motion of a particular disk at a pointproximate to a corresponding head reading from or writing to the disk,the system moves that head to compensate for the motion of the disk. Asa result, the relative motion of the head with respect to thecorresponding disk is reduced or eliminated.

In one implementation, a voice coil motor (VCM) that normally engagesand operates the head utilizes information provided by the detector headand/or other logic to move the head in response to movement of the disk.In this aspect, the head is substantially-rigidly coupled to an arm thatmoves under control of the VCM. In an alternative implementation, thehead is mechanically coupled to a first end of the arm controlled by theVCM via a jointed connection, and the head may move with respect to thefirst end of the arm under the control of one or more actuators.

The method for averaging out random errors by writing different segmentsof a track in multiple revolutions disclosed herein may be utilized inconnection with one or more heads writing information to a disk. Whenmultiple heads are utilized to write to a single disk, the heads may bedistributed along a single arm controlled by a single VCM. Each head maybe individually controlled by one or more corresponding actuatorsmechanically coupled to the arm. Alternatively, there may be more thanone arm, and each arm may be controlled by the same or different VCMs.

While the description above has provided an example of how an aspect ofthe present invention may be employed to produce an ideal magnetic disk,the methods and systems disclosed herein may also be applied to produceregular data disks. More specifically, the systems and methods taughtherein may be utilized by a commercial system to write data to a diskprior to distribution of the disk to an end user, or by a disk drivecomprised in a system utilized by an end user. The systems and methodsdisclosed herein and discussed in connection with FIGS. 7-10 may beemployed to improve the accuracy with which data tracks are written in avariety of applications, aside from certification, initialization andservo writing of disks. For example, but without limitation, a desktopor a laptop computer system may comprise a disk drive that utilizesmethods and systems taught herein to improve the reading and/or writingof regular data from and/or to a disk, such as operating systeminformation, software and word processing files. As another example, aportable consumer device may employ methods and systems taught herein toimprove storage and/or retrieval of data to and/or from a disk,including audio, video, and/or communication data.

Certain modifications to the methods and systems disclosed herein may bemade while remaining within the scope of the present aspects of theinvention to more appropriately address particular characteristics ofthe intended application. For example, in a mobile consumer device thatmay be commonly and repeatedly exposed to physical shocks due tophysical impacts or movements, the expression of the energy E and/or thecorresponding thresholds may be altered to tolerate a wider range ofdeviations in the position, shape, or other relevant characteristics ofthe data tracks, possibly at the expense of track density.

3. Non-Contact Radiation Detection System that Bounces Radiation Off aPart of the Spindle

Yet another aspect of the invention provides a system and method fordetecting movement of a spindle and/or one or more disks with respect toa common base by detecting radiation reflected by a part of the spindle.Movement of the spindle and/or one or more disks with respect to thecommon base may then be related to movement with respect to one or moreread/write heads.

As described above, movement of the spindle with respect to the base mayresult in relative movement between a disk and a corresponding headwriting to, or reading from the media disk, thereby possibly interferingwith the operation of the head. In one embodiment, the system detectsthe magnitude and direction of such movement between a disk and acorresponding head and compensates for such movement by moving the headaccordingly.

One implementation of this aspect of the invention utilizes a sourcethat directs radiation towards an area of the spindle and a receiverthat detects radiation reflected by the area of the spindle. Hardwareand/or software logic functionally connected to the transmitter and/orreceiver detects movement of the spindle with respect to the base andmoves one or more heads reading from, or writing to the disksaccordingly.

In one aspect, the non-contact radiation detection system comprises anoptical system. The optical system comprises an optical transmitter,such as a laser diode, and an optical receiver, such as an opticaldetector. The optical transmitter and receiver are disposed or otherwisefixedly mounted to the base of the equipment and cooperate to detectmovement (other than normal spinning) of the spindle with respect to thebase.

A cylindrical area of the spindle exhibits a certain degree ofreflectivity. In one case, the cylindrical area is manufactured from areflective metal, such as steel, and is polished to exhibit a relativelyhigh degree of reflectivity. Alternatively, the cylindrical area of thespindle may be covered with a reflective material. The cylindrical areaof the spindle is substantially perpendicular to the planar surfaces ofthe disks stacked on the spindle. The spinning axis of the disks stackedon the spindle is substantially parallel with the cylindrical area andapproximately coincides with the central axis of the cylindrical area.Both the cylindrical area and the stacked disks are substantiallyrigidly connected to the spindle, such that the cylindrical area and thestacked disks spin with approximately the same angular speed.

The optical system detects movement of the spindle with respect to thebase by illuminating the reflective cylindrical area with a laser beamproduced by the optical transmitter and receiving a reflected portion ofthe laser beam at the optical detector.

Cross sections of the cylindrical area may not be perfectly circular,but may exhibit irregularities, such as an oval, non-circularly-curved,or “egg” shape. To compensate for any imperfections in the surface ofthe cylindrical area, the system in one aspect analyzes the Fourierfrequency spectrum of the light reflected off the cylindrical area andfilters out periodic signals that may be attributed to imperfections ofthe cylindrical surface intercepting the incident laser beamperiodically as the spindle spins at a relatively-high rate.

Another aspect of this reflective spindle configuration utilizes two ormore laser beams offset with respect to each other. Each laser beamcorresponds to a dedicated laser source and a dedicated laser detector.Since imperfections of the cylindrical surface will exhibit similarsignatures on each laser beam, as detected by the various correspondinglaser detectors, these imperfections may be filtered out and the actualmovement of the spindle with respect to the base may be isolated anddetected or estimated.

One alternate aspect of the invention in addition to those outlinedabove is using a series of ridges or non-reflective material equallyspaced around the cylinder such that light energy transmitted to thecylinder reflects efficiently off reflective areas but does not reflectefficiently off the ridged or nonreflective areas. This enables thesystem to measure relative position and timing and correct errors bycounting the number and time of reflections provided.

Hardware and/or software logic may utilize variations in the intensity,frequency and/or phase of each reflected laser beam received at thecorresponding detector to determine the magnitude and direction ofmovement at any point along the spindle or on the disks, both withrespect to the base and with respect to any heads operating on thedisks. The system can determine such parameters using an interferometerto detect movement of the spindle.

Once the direction and magnitude of motion of a particular disk isdetermined at a point proximate to a corresponding head reading from, orwriting to the disk, the system moves the head to compensate for themotion of the disk. As a result, the relative motion of the head withrespect to the disk is minimized or eliminated. In a particularimplementation, a voice coil motor (VCM) that normally engages andoperates the head utilizes information provided by the optical systemand/or other logic to move the head in response to movement of the disk.In this aspect, the head may be substantially-rigidly coupled to an armthat moves under control of the VCM. In an alternative implementation,the head is mechanically coupled to a first end of the arm controlled bythe VCM via a jointed connection, and the head may move with respect tothe first end of the arm under the control of one or more actuators.

According to an embodiment of the invention, multiple heads are utilizedto write to a single disk, and the heads may be distributed along asingle arm controlled by a single VCM. Each head may be individuallycontrolled by one or more corresponding actuators mechanically coupledto the arm. Alternatively, there may be more than one arm, and each armmay be controlled by the same or different VCMs. In each of theseimplementations, the system may utilize the information obtainedregarding the magnitude and direction of relative movement between aparticular head and a corresponding disk to reposition the head and/ordisk dynamically.

An alternative aspect of spindle position measurement provides alternatedifferential systems to detect spindle movement with respect to thebase. The differential system for detecting motion of the spindle may,for example, comprise two or more laser beams reflecting off differentportions of a reflective or alternating reflectivity/nonreflectivitypart of the spindle to detect the magnitude and direction of spindlemovement at different points in the system.

As a further feature of the present design, the system performs variousfunctions designed to minimize repeatable run out and/or non repeatablerunout errors (RRO and NRRO). RRO and NRRO are measurements of theradial accuracy of written tracks. RRO and NRRO measurements may beperformed after the system has written to the disk, and can be assessedby assembling the written disks into drives and testing. Components suchas the spindle may also be tested independently to insure runout erroris within predetermined specifications, but this again typically occursafter the write operation. Such measurements are generally not madeduring the servowriting process. In some cases, a few basic runoutperformance values can be made available after writing the servo patternby reading the radial positioning error with the same magneticread/write head on the servowriter used to write data. The system thenrecords the standard deviation of the RRO and NRRO for the just-writtentracks.

The present system monitors runout performance during servowriting. Therunout error signal may be used for a follow up correction indication sothat improperly written data, such as a servo mark, can be rewritten.Rewriting miswritten data tends to limit the tail of the runout errorstatistical distribution, thereby enabling tighter overall errordistribution and therefore smaller track spacing.

For simultaneous monitoring of radial track positioning errors, thesystem generally cannot use the read/write head during the writingprocess. Various supplemental optical or capacitive sensors monitor thespindle axis position with respect to a base, reference spindle axisposition, or a surface that emulates the head position with respect tospindle axis position. This relative measurement may be performed using,for example, a single beam or differential beam interferometer asdiscussed herein. Other routine position monitoring devices such ascapacitance probes, inductive sensors or alternate optical positionsensors could also be employed to monitor spindle position.

Performance metrics for track writing performance may be expressed interms of the standard deviation of radius from a demanded radius. Thisstandard deviation can be separated into repeatable and nonrepeatablecomponents for purposes of measuring/correcting. In addition, numerousmonitoring and performance metrics have not been previously implementedon data writing devices such as servowriters.

An aspect of the invention provides a method and system fordetermination of a monitoring and performance metric for assessing trackdata: the time or RPM dependent servo mark positions, or opticallyinferred spindle axis position. Since disks are mechanically coupled tothe spindle, the position of the axis of the spindle may be reliablycorrelated with the position of a servo mark located on any particulardisk, and such a correlation is bi-directional in the sense that knowingeither of the two enables determination of the other one.

According to various aspects of the present invention, assessing time orRPM dependent servo mark positions or optically inferred spindle axispositions can be accomplished in different ways. In a particularimplementation, an optical sensor can be used to monitor the position rof the spindle chuck or hub surface and record r(θ(t)) as the spindlechuck spins with angular velocity ω. The topographical radiusr_(t)(θ)=r_(t)(ωt) of the surface as a function of angle θ can bedetermined independently. The difference:δr(t)=r(θ(t))−r _(t)(θ)

expresses the amount of wobble in the disk axis. This wobble can bedivided into two components: a repeatable part having harmonics of thebasic rotational rate given by the following Fourier componentsA _(N)(ω)=(2π)⁻¹Σ_(i) exp(iNωt _(i))δr(t _(i));δr _(rro)(t _(i))=τ_(N) exp(−iNωt _(i))A _(N)(ω).

and a non repeatable part including nonharmonic componentsδr _(nrro)(t _(i))=δ_(r)(t _(i))−Σ_(N) exp(−iNωt _(i))A _(N)(ω)

With respect to the repeatable portion, A_(N)(ω) is the amplitude of thespindle wobble at a frequency of Nω. This value may not be constant butmay change slowly with time. The media writer or servo writer has theability to monitor this amplitude during writing for process control,grading, media writer self testing, or for actively controlling themedia writer as disclosed herein using this repeatable portionamplitude. For example, active control of the media writer may occur byputting a deflection on the voice coil to place a compensating positionon the writer head.

Another example of employing processed data in servowriting performanceis using the histogram of the NRRO component (non-repeatable part of thewobble that includes the nonharmonic components) of the servo markpositions or optically inferred spindle axis position. In thisarrangement, an optical sensor such as an interferometer monitors thesenon repeatable errors during servowriting. The width and shape of thisdistribution assesses data writer performance as well as the quality ofthe servo patterns on the disk.

4. Radial Positioning Using Interferometer

Yet another aspect of the invention provides a system and method fordetecting movement of a spindle and/or one or more disks with respect toone or more read/write heads by detecting radiation reflected by both apart of the spindle and one or more features mechanically coupled to oneor more of the heads. One embodiment of the invention employs aninterferometer in performing radial positioning functions. The presentdesign enables in-situ monitoring of the disks and allows certificationby offering dynamic compensation for spindle movement.

In an alternative implementation, information regarding movement of thespindle and/or heads with respect to a common base obtained aspreviously described may be employed together with data obtainedaccording to the embodiment further described in this section to furtherimprove the accuracy and/or reliability of the measurements.

In common implementations, interferometers are devices that convert thephase difference between two input waves into intensity variations onone or more output waves that carry information about the phasedifference between the input waves. The interferometer outputs mayrepresent superpositions of portions of the two input waves. The amountof each input delivered to each output and the phase shift impartedduring delivery correlates to the optical path length difference betweenthe two beams.

One type of interferometer that may be used in the present system isthat described in U.S. patent application Ser. No. 09/______, entitled“Waveguide Based Parallel Multi-Phaseshift Interferometry for High SpeedMetrology, Optical Inspection, and Non Contact Sensing,” inventors DavidPeale, et al., assigned to the assignee of the present invention, whichis hereby incorporated by reference into the present application. Theinterferometer of this aforementioned application is a multiphaseinterferometer that employs waveguided optics and an optical coupler toproduce a tri-phase signal that enables measurement of phase differencesbetween two emitted beams.

One aspect of the invention disclosed herein is to measure the distanceof the head to the disk axis, or spindle, as accurately and directly aspossible. Direct measurement comprises using as actual a distancemeasure of the head position as possible, with as little indirect orcalculated measurement as may be performed under the circumstances. Oneaspect of the present invention is illustrated in FIG. 11. From FIG. 11,the system employs an optical interferometer transmitting two laserbeams in a differential mode. Interferometer 1101 comprises a laserlight generating source, and possibly more than one such source, togenerate two separate laser beams. The first laser beam strikes a firstlens 1102 and a second focusing lens 1103 and directs the resultant beamto the polished chuck 1106. Polished chuck 1106 typically comprises ahighly reflective or mirror like surface. The second beam passes throughthird lens 1104 and is retro reflected from a corner cube 1105 or otherretro reflecting surface mounted on the e-block, illustrated in FIG. 4as element 404. A corner cube, or cat's eye, operates under the law ofreflection, but operates differently from a typical mirror or reflectivesurface. A beam of light entering the corner cube is reflected back inthe same general direction as its angle of entry. This same-directionreflection occurs for not only one special angle of incidence with amirror, but for all angles of incidence with the corner cube. The secondbeam in FIG. 11 is typically collimated, or emits energy waves that aresubstantially parallel. Mounting the retro element, such as corner cube1105, to the e-block, is performed in an orientation that emulates thehead position. In other words, the retro reflective element is mountedin a position on the positioner or e-block that emulates the position ofthe read/write head, and the stiffness of the positioner arm andconnection between the e-block position and the read/write head offers asubstantial analogy to actual head position. The retro reflector orcorner cube 1105 swings in an arc tangent to the second, substantiallycollimated, interferometer beam, and reflects back through third lens1104 and back to the interferometer, where the time of reflection ordistance from the interferometer 1101 to the emulated head position isdetermined. The resultant interferometer signal substantially measuresthe distance between the surface of the chuck or chuck spindle 1103 andthe simulated head position at the retro reflector or corner cube 1105.The difference between the interferometer and the chuck minus thedistance between the emulated head and the interferometer is δraw, orthe raw measurement of head position relative to the polished chuck1106.

The difference signal δraw must be corrected for topological parametersof the polished chuck 1106. The chuck 1106 can deviate from a perfectand exactly centered cylinder, and under certain circumstances may moveor shift during operation. The system measures deviation independentlyas a function of disk angle, Θ, and the measurement is dynamicallystored in memory. Deviation of the cylindrical chuck is represented byδtopo(Θ). The system then computes the error signal based on thedifference between the raw position of the emulated head minus thetopographical error of the disk cylinder, δerr=δraw−δtopo(Θ). This errorsignal is employed by the system to actuate the voice coil 1107 andmicro actuators on the suspension to reposition the head to moreaccurately track the radius of the true axis of the disk. The errormeasurement is factored into the desired position of the head to affectmovement of the head to a more exact position over the disk. Inaddition, that portion of the error signal at frequencies too high forthe positioning servo to correct for can be used to inhibit writing ofthe servo information if this signal is above a predetermined limit.Writing of the servo information may recommence once the error signalfalls below the limit.

In an alternate aspect of the present design, an additionalinterferometer is employed above the disk to provide a z-axismeasurement and to address issues of tilt. In this embodiment, the retroreflector or corner cube is located at a different height than thelateral version to measure differential z position caused by tilt. Thesecond interferometer also uses lensing to set up a collimated beam andtracks a reference Z point, which may be disk position or spindlelocation, or some other available reference height point on thearrangement. The measurement at an additional axial position (z) is fedback to the signal processor and the voice coil is employed to correctthe head position over the disk. If the system measures the tilt of arotating spindle, signal processing requires the raw positional zmeasurement minus the topographical shift resulting from tilt. Dependingon the parameter desired to be measured, whether head position, spindleposition, or disk position, the retro reflector must be positioned tooffer an accurate representation of the target parameter. Thus if zposition of the head is the desired parameter to be measured, the retroreflector positioning must, like the aspect described above, emulate thehead position, such as on the e-block or otherwise associated asdirectly as possible with the positioner and/or read/write head.Alternately, if tilt of the spindle is the desired measured parameter,one beam may reflect off approximately the top center point of thespindle, for example, while the second beam reflects off a point as farto the periphery of the spindle as possible.

In another alternate aspect of the present system, a second lateralinterferometer is used with the system illustrated in FIG. 11, with a 90degree difference between the first interferometer and the second tomeasure y axis movement in addition to x axis movement.

Unless indicated or implied otherwise, as used herein, x and ydirections are conventionally assumed to indicate directionssubstantially in the plane of a particular disk, while the z directionindicates a direction substantially parallel with the axis of thespindle. In particular embodiments, more than one substantially-parallelx-y planes may be considered when more than one disk is coupled to thespindle. Depending on the context, the angle theta (θ) may beconventionally defined in a particular x-y plane, or may be aspindle-characteristic value that is common to all disks coupled to thespindle.

This aspect of the invention uses an additional retro reflector orcorner cube mounted on the e-block or other available and practicallocation to emulate head position and retro reflect the incomingcollimated beam. The interferometer again passes energy through alensing arrangement to focus and/or collimate the beams, and one beam isalso directed toward the spindle arrangement. This x-y dualinterferometer arrangement provides additional accuracy, and similarparameters are fed to the signal processor and used to command the voicecoil to more accurately position the e-block, positioner, and associatedread/write heads.

An embodiment of a system employed as taught herein to attain highaccuracy positioning may include a dual beam interferometer as describedin the Peale application, U.S. patent Ser. No. 09/______. The Pealedesign uses a tri-coupler where the reference beam of the tri-coupler iscollimated onto a retro-reflector mounted to the E-Block describedpreviously and the other beam is focused onto the spindle hub.

More specifically, the guided wave interferometer is a system comprisesa tri-coupler and has the following aspects. The tri-coupler consists ofthree waveguide inputs, three waveguide outputs, and a region betweenthe inputs and outputs wherein waves from each of the three inputs areredistributed approximately equally to each of the three outputs.Assuming that the tri-coupler is lossless and distributes light from aninput waveguide equally to each of the three output waveguides, thenthere may be a 120 degree phase shift between each of the three outputlight waves. Thus, if light is injected into two of the inputwaveguides, the intensity of the light in the three output waveguideswill possess a periodic interferometric modulation as the phasedifference between the input beams advances, and in particular, thephase relation among the intensities of these three beams will be 120degrees. It is thus possible to measure the intensities of the threeoutput beams, and accurately determine the phase difference between thetwo input beams. In addition, the total intensity of the input light canalso be calculated.

Referring to the drawings more particularly by reference numbers, FIG.14 is a schematic cross section through one section of a fused-fiberoptical tri-coupler 10 showing the spatial symmetry of the three fibers12, 14 and 16, leading to the characteristic 120 degree phase relationbetween the light waves within each of the three waveguides. Thetri-coupler 10 couples light between the first 12, second 14 and third16 waveguides such that light input at one end of any waveguide issubstantially equally distributed to each of the three waveguides at theoutput end.

FIG. 15 shows an embodiment of an optical interferometer 50 of thepresent invention. The interferometer 50 may include a first waveguide12, a second waveguide 14 and a third waveguide 16. The waveguides maybe fiber optic cables or integrated waveguides that transmit light.

One of the waveguides, namely the second waveguide 14, may be coupled toa light source 18. By way of example, the light source 18 may be alaser. The light source 18 may have a return isolator 19 that preventsback reflections from feeding back into the source 18. The light emittedfrom the light source 18 and isolator 19 may be directed into thetri-coupler 10 via an optical circulator 22.

Light entering the tri-coupler 10 along waveguide 14 is distributed toeach of the three output waveguides in roughly equal intensities. Lightexiting the tri-coupler on waveguide 14 is allowed to escape thewaveguide unused, and the waveguide is terminated in such a way thatminimal light is reflected back into the tri-coupler. The light exitingthe first waveguide 12 is reflected from an object surface 24 back intothe waveguide 12. The interferometer 50 may include a lens assembly 26and autofocus system 38 that focuses the light onto surface 24 and backinto waveguide 12. Light within the third waveguide 16 may be reflectedfrom a reference surface 27 back into the waveguide 16. The object 24and reference 27 surfaces may be separate locations of the same testsurface. Alternatively, the light from the third waveguide 16 may bereflected from a reference surface (not shown) separate from the objectsurface 24.

The light reflected from the test surface 24 and reference surface 27through the first 12 and third 16 waveguides travels back through thetri-coupler 10. The reflected light within the first waveguide 12provides an object beam. The light within the third waveguide 16provides a reference beam that interferes with the object beam withinthe tri-coupler 10.

The tri-coupler 10 allows reflected light within the first waveguide 12to be coupled into the second 14 and third 16 waveguides, and reflectedlight from the third waveguide 16 to be coupled into the first 12 andsecond 14 waveguides. The output of the tri-coupler 10 is three lightbeams with intensities that are out of phase with each other byapproximately 120 degrees. The light intensity of each light beamdetected by photodetectors 28, 30, and 32. The light exiting thetri-coupler along waveguide 14 is directed to the detector 28 via thecirculator 22.

Photodetectors 28, 30, and 32 provide electrical output signals to thecomputer 34. The computer 34 may have one or more analog to digitalconverters, processor, memory etc. that can process the output signals.

By way of example, the interferometer 50 can be used to infer thedistance between the retro-reflector mounted on the E-Block and thesurface of the spindle hub where the surface of the spindle hub 24 is atthe focus and the retro-reflector 27 returns the collimated beam.

The differential distance (modulo λ/2) at any point can be inferred fromthe following equation.h=λ*θ/4π  (1)where:

h is the apparent differential distance;

θ is the interferometric phase angle between the object and referencebeams, and

λ is the wavelength of the reflected light.

The interferometric phase angle can be determined by solving thefollowing three equations.I1=α1(E1²+(β1E2)²+2β1E1E2 cos(θ−Φ1))  (2)I2=α2(E1²+(β2E2)²+2β2E1E2 cos(θ−Φ2))  (3)I3=α3(E1²+(β3E2)²+2β3E1E2 cos(θ−Φ3))  (4)where:

I1=is the light intensity measured by the photodetector 28;

I2=is the light intensity measured by the photodetector 30;

I3=is the light intensity measured by the photodetector 32;

E1=is the optical field of the light reflected from the test surfaceinto the first waveguide 12;

E2=is the optical field of the light reflected from the test surfaceinto the third waveguide 16;

Φ1=is the phase shift of the detected light within the first waveguide,this may be approximately −120 degrees;

Φ2=is the phase shift of the detected light within the second waveguide,this may be defined to be 0 degrees;

Φ3=is the phase shift of the detected light within the third waveguide,this may be approximately +120 degrees;

α1=is a channel scaling factor for the first waveguide and detector;

α2=is a channel scaling factor for the second waveguide and detector;

α3=is a channel scaling factor for the third waveguide and detector;

β1=is a coupler nonideality correction term for channel 1;

β2=is a coupler nonideality correction term for channel 2, and

β3=is a coupler nonideality correction term for channel 3.

The interferometer 50 may include a phase shifter 36 that shifts thephase of the light within the third waveguide 16. The phase shifter 36may be an electro-optic device that can change the phase to obtain anumber of calibration data points. The calibration data can be used tosolve for the phase shift values Φ1, and Φ3, the channel scaling factorsα1, α2, and α3, and the coupler nonideality factors β1, β2, and β3. Thevalues are stored by the computer 34 and together with the measuredlight intensities I1, I2, and I3 are used to solve equations 1, 2, 3,and 4 to compute the phase angle, θ and the apparent distance h.

FIG. 16 shows an alternate embodiment of an optical interferometer 60 ofthe present invention. The interferometer 60 uses a 2×2 optical coupler23 in place of the circulator 22 used in interferometer 50. In thiscase, light from the laser is split as it passes forward through coupler23. Light exiting coupler 23 along waveguide 15 is discarded. Lightexiting coupler 23 in waveguide 13 is fed into tri-coupler 10 as in theinterferometer 50 previously discussed. Light returning from tri-coupler10 along waveguide 13 is split. Light exiting coupler 23 along waveguide13 is rejected by isolator 19 and does not interfere with the laser.Light exiting coupler 23 along waveguide 15 is fed to detector 28. Thisembodiment of interferometer 60 may be less expensive to produce thanthat of interferometer 50 owing to the fact that coupler 23 may beconsiderably less expensive than circulator 22. However, the laser powerdelivered into the tri-coupler 10 may be correspondingly reduced and thesignal detected by detector 28 may also be reduced as compared to thosedetected in detectors 30 and 32.

The output signals of the photodetectors 28, 30, and 32, responding to asteadily advancing phase angle at the inputs, are shown superimposed inFIG. 17. The phase shifts between different light beams separates themaxima and minima of the output signals. With such an arrangement atleast one of the signals will be in a relatively sensitive portion ofthe waveform between a maximum and minimum. This illustrates how thepresent invention provides an interferometric detector that has arelatively uniform sensitivity and is therefore desirable formetrological applications.

Interferometers 50 and 60 of the present invention provide threeout-of-phase signals with a minimal number of parts. The tri-coupler 10and fiber optic waveguides 12, 14, and 16 can be packaged into arelatively small unit, typically measuring only 0.12 inches diameter bytwo inches in length. This reduces the size, weight and cost of theinterferometers. By way of example, the tri-coupler 10 and waveguides12, 14, and 16 could be also constructed onto a single planar substrateusing known photolithographic and waveguide fabrication techniques. Sucha construction method would have advantageous properties which wouldallow tighter integration with other portions of the interferometricsystem together with reduced assembly costs.

As an alternative to those aspects discussed herein usinginterferometers, other sensing means or sensors may be employed todetect head position, using independently positioned detectors. Such aconstruct may employ fiber optics where the fibers are in closeproximity to the head and/or spindle. In such a design, the position ofthe spindle and heads are generally known to a degree. Light energy orother energy may be directed toward, for example, a head, and energyreflected off the head and received by a sensor located proximate ornear the head in the zone of expected energy reflection. Capacitancesensors or inductive sensors could also be employed in the design. Ingeneral, any three independent position detectors could be used todetect head position or spindle position in this design.

The present aspect of the invention is not limited to the specificconstructions and arrangements shown and described, since various othermodifications may occur to those ordinarily skilled in the art. Forexample, although the light reflected from the test surface 24 isinitially directed through the tri-coupler 10, it is to be understoodthat the light can be introduced to the test surface 24 withoutinitially traveling through the coupler 10.

Adjustment of Spindle Position

Various aspects of the invention described herein provide methods andsystems for directly on indirectly determining relative motion betweenone or more heads and one or more corresponding disks. In a typicalcase, one or more heads are operationally coupled to a disk reading toor writing from the disk, and a system provided by an embodiment of thepresent invention attempts to accurately position the one or more headson the disk by identifying and minimizing or eliminating positionalerror interferences. In particular embodiments, the system operatessubstantially simultaneously on more than one disk. In the embodimentspreviously disclosed, correction of positional errors has been generallyachieved by repositioning the heads.

An aspect of the present invention provides an alternative method forcorrecting positional errors between heads and disks, namely, ratherthan repositioning a head, the system may reposition the spindle.Alternatively, the system may reposition both the head and the spindle.In a general case, according to an embodiment of the invention, thesystem may reposition each head in the system while,substantially-simultaneously, also repositioning the spindle. In thisgeneral case, there may be more than one head operationally coupled toeach disk, and each of these heads may be individually repositioned.

Cooperative repositioning of heads and spindle may help reduce oreliminate positioning errors with respect to each disk on which thesystem operates, and therefore may improve reading and writing of datato each such disk. In a servowriting and/or certification system, butalso in any other commercial or end user system or application, this mayimprove system performance, such as increasing the track density and thethroughput, and may reduce costs.

In one embodiment, as the system tracks positioning errors for each diskand head in the system, the system may elect to solely reposition thespindle without repositioning any of the heads in the system. This mayoccur when the system determines that repositioning of the spindle maysatisfactorily reduce all or sufficiently many of the positional errorsassociated with individual heads in the system without repositioning anyof the individual heads. This may be a more efficient and fastersolution to correcting positioning errors during operation of the systemas compared to individually adjusting the position of individual heads.

Movement of the spindle may be an effective approach to resolverepeatable run out errors. One cause for repeatable run out errors is animbalance in the mass distribution of the spindle and disks. An aspectof the invention may reduce positioning errors attributed to repeatablerunout by addressing and attempting to compensate for imbalances in thespindle and/or disk mass distribution.

Various embodiments of the invention provide methods and systems forrepositioning a spindle to address positioning errors in the system.Once an error is detected, the spindle may be moved using conventionalmeans while rotating, including but not limited to using anelectromotive force (EMF) to alter spindle position. In oneimplementation, the spindle motor that normally drives the spindle torotate the disks coupled to the spindle may move the spindle in anyarbitrary direction. For example, the spindle motor may move the spindlealong the spindle axis, in the plane of any particular disk coupled tothe spindle, or in an arbitrary three dimensional spatial direction.Such an arbitrary three dimensional direction may include displacementboth in a plane that substantially comprises the spindle axis and in anx-y plane that substantially comprises the surface of a particular diskcoupled to the spindle.

In one embodiment, the spindle may be moved by altering the currentthrough the spindle motor coil. In one embodiment, the spindle may bemoved using one or more electromagnets disposed in proximity of thespindle to interact with the spindle and move the spindle via a magneticfield. In one implementation, at least three external electromagnets aredisposed around the spindle, and the three electromagnets cooperate toproduce magnetic fields of arbitrary orientations and intensities thatmay move the spindle in any three dimensional arbitrary direction. Inone embodiment, permanent magnets are mechanically coupled to thespindle to interact with the external electromagnets. In anotherembodiment, one or more spindle electromagnets are mechanically coupledto the spindle to interact with the external electromagnets.Electromagnets coupled to the spindle may also interact with externalpermanent magnets. Any combination and number of permanent magnets andelectromagnets may be mechanically coupled to the spindle and/ordisposed along the spindle. To reposition the spindle, the system mayvary electric currents through such spindle or external electromagnetsto produce appropriate variations in the magnetic fields interactingwith the spindle, thereby moving the spindle as desired.

Various devices may be utilized as electromagnets, including HelmholtzCoils, magnetic coils with or without cores, and others. Generally, anddevice or combination of devices that produce a magnetic field with anadjustable intensity, gradient, and/or orientation may be utilized asdescribed herein to move the spindle. Some of the embodiments disclosedherein insulate sensitive system components from the magnetic fieldsproduced by permanent magnets and/or electromagnets to avoidinterference. The system components that may be protected from magneticfields include actuators, read and/or write heads, and other componentssensitive to electromagnetic interference.

According to an aspect of the invention, a spindle may also be movedmechanically, via physical forces. In one aspect, variable air pressurethrough the orifices of the air bearing could be employed to control andcorrect spindle positioning.

An embodiment of the invention utilizes actuators embedded in thespindle to redistribute the mass of the spindle and disks. In one case,if the system determines an imbalance in the mass distribution of thespindle that produces a repeatable run out error on one or more disks,the system may activate one or more actuators disposed along the spindlesubsystem to rebalance the mass distribution. This may be achieved byextending and/or retrieving one or more objects via actuators withrespect to the spindle axis. In a particular implementation, forexample, the system may extend an actuator beyond the circumference ofthe rotating spindle, thereby adding mass in a particular radialdirection of the spindle. Adding mass in particular radial direction ofa rotating spindle would increase the local centrifugal force, therebyproducing an additional local force, which could be utilized to move thespindle. The reverse effect could be achieved by retrieving an actuatorinside the circumference of a rotating spindle, thereby decreasing thelocal centrifugal force.

One embodiment may include altering spindle position by interacting withthe spindle via particles that exhibit mass. In a particularimplementation, the system may utilize air bursts or other fluid burstsproduced by one or more sources disposed in proximity of the spindle tomove the spindle. Such an arrangement may employ a nozzle or nozzles,and may require submerging the spindle and/or media in fluid.

According to an aspect of the invention, any combination of the methodsand systems disclosed above for moving a spindle may be utilized toreposition the spindle alone, or in further combination withrepositioning of any group of one or more individual heads. For example,in one case, mechanical actuators may be employed to rebalance a spindlesystem exhibiting a mass-induced repeatable run out error, while acombination of magnetic devices actively reposition the spindle andindividual heads are repositioned with respect to particular disks.

Multiple Sector Servo Writing

Another aspect of the invention disclosed herein seeks to improve diskmanufacturing yield by writing multiple sets of servo sectors or datasectors to the disk in a single revolution and then selecting the set ofservo sectors exhibiting the highest data integrity. This aspect of thepresent invention applies to various types of data storage employingcircular media, including but not limited to magnetic disk systems,optical disk systems, and the like. The use of a single revolution towrite data to circular media and subsequent selection of specificsectors of the media is applicable to any circular media writing system.

An aspect of the current invention provides a method for increasingmagnetic disk yield during the manufacturing process. During the mediadisk formatting phase, the system writes a set of servo sectors to thedisk to provide a structure that guides writing and/or reading of datato the disk in subsequent phases. Generally, the number of servo sectorson a particular disk is the same as the number of data sectors.According to one embodiment, each servo sector 1201 corresponds to adata sector and is comprised within the data sector 1202 as shown inFIG. 12. Conventionally, the servo sector 1201 is located at thebeginning of the data sector, as perceived in the angular direction ofrotation of the disk. Physically, both the data sector 1202 and theservo sector 1201 are shaped as partial substantially-circular sectors,but the servo sector 1201 subtends a significantly lower angle andoccupies a correspondingly lower overall area. The servo sectorscomprised in the set of servo sectors written to the disk during theformatting stage are disposed at substantially regular angular offsetpositions around the disk, a representation of which is illustrated inFIG. 13. More or fewer servo sectors may be written to the diskdepending on system requirements, but the important characteristic ofthis aspect of the invention is that servo data is disposed around thedisk during this single revolution initial formatting stage.

According to an aspect of the present invention, once the system haswritten the set of servo sectors to the disk, the servowriter verifiesdata written in the servo sectors to validate the disk. If the datawritten within the servo sectors exhibits sufficient integrity, theservowriting process is considered successful, and data sectorscorresponding to the servo sectors are produced and validated. The datasectors may store data subsequently written to the disk.

According to an aspect of the present invention, more than one set ofservo sectors is written to the disk in the formatting phase, preferablyduring the same revolution. As a result, instead of a single set ofservo sectors disposed at substantially regular angular positions aroundthe disk as shown in FIG. 13, the method disclosed herein produces oneor more additional sets of servo sectors, each of these servo sectorsbeing also disposed at substantially regular angular positions aroundthe disk with respect to other servo sectors within the same set.Alternatively stated, this method produces duplicates of the originalset of servo sectors, wherein each servo sector comprised in a duplicateset is offset by a constant angular amount with respect to acorresponding servo sector in the original set of servo sectors. Forexample, if the original set of servo sectors comprises a total of 36servo sectors, the beginning of each servo sector is offset from thebeginning of the preceding servo sector by ten degrees. A duplicate setof servo sectors would comprise a total of 36 duplicate servo sectors,and each of these duplicate servo sectors would be offset with respectto the preceding duplicate servo sector by ten degrees. If, for example,the duplicate set of servo sectors is disposed on the disk such that aparticular duplicate servo sector is offset from a particular originalservo sector by three degrees, each subsequent duplicate servo sectorwill also be offset from a corresponding original servo sector by threedegrees. In an alternative implementation, individual servo sectors maybe offset at arbitrary intervals, but the system may need to store moreinformation regarding the actual position of such servo sectors.

Upon writing one or more duplicate sets of servo sectors to the disk,the system proceeds to verify the integrity of the data written to eachservo sector. One way of verifying the integrity of this data is to readthe data and compare it against the data originally written to the disk.The system then selects the set of servo sectors exhibiting the highestdegree of data integrity and erases or discards all other servo sectors.Depending on the result of the verification process, the system mayelect to retain the original set of servo sectors, or may retain one ofthe duplicate sets of servo sectors. After erasure, the disk may beremoved from the servowriter and located in a hard disk drive, or if ina disk drive originally, the disk may remain therein and operatenormally. The system comprising the media disk may then utilize theselected set of servo sectors as a basis for further operations on thedisk, including data storage to the disk.

Another aspect of the invention utilizes the writing and readingconcepts disclosed above to increase the data storage capacity of a diskby writing multiple duplicate versions of data to the disk in differentdata sectors around the disk, and then retaining only the dataexhibiting a sufficient degree of integrity. This aspect of theinvention applies the method described above to regular data commonlystored on magnetic disks, such as computer operating system data or aword processing file stored on a hard disk, rather than just to servodata. In this aspect of the invention, similar to the servowritingaspect outlined above, more than one set of data sectors is written tothe media disk during normal operation, preferably during the samerevolution. As a result, instead of a single set of data sectorsdisposed at predetermined positions around the disk based on availablespace on the disk, this aspect of the method disclosed herein producesone or more additional sets of data sectors, each of these data sectorsbeing also disposed at predetermined and available positions around thedisk with respect to other data sectors. The system in this aspect ofthe invention writes data, here called “associated data,” to availableareas of the disk using an associated data header to indicate thebeginning of the data area. As used herein, the term “associated data”indicates data located on a media disk surface typically associated withother data on said media disk surface, as differentiated from the term“data,” which indicates data generally, associated or unassociated.Associated data subsets are located at available positions around thedisk with information correlating such associated data with similarlyassociated data. The system writes a second set of data with apredetermined header indicating the beginning of said data and writesthe remaining data around the disk to available locations. Data includedin this second group may be spaced at different locations around thedisk, but the data is associated with the second group and second headersuch that it can be retrieved appropriately. The result is two identicalsets of data written to the disk, with header information indicatingthat the associated data is identical but separate, along withinformation specifically associating the separate but identicalgroupings of associated data.

Alternatively stated, this method produces duplicates of the originalset of data sectors, wherein each data sector in a duplicate set isoffset with respect to a corresponding data sector in the original setof data sectors. The data sectors are not necessarily equally offsetfrom one another, but rather may be randomly offset and broken apart indifferent configurations.

Upon writing one or more duplicate sets of data sectors to the disk, inone embodiment, the system proceeds to verify the integrity of the datawritten to each data sector. One way of verifying the integrity of thisdata is to read the data and compare it against the data originallywritten to the disk. The system then selects the set of data sectorsexhibiting the highest degree of data integrity and erases all redundantdata sectors. Depending on the result of the verification process, thesystem may elect to retain the original set of data sectors, or mayretain one of the duplicate sets of data sectors, including the relevantheader information and association data. Once the disk has been erased,the disk may be operated normally. The system where the media disk isintegrated then utilizes the selected set of data sectors as a basis forfurther operations on the disk, including data storage to the disk.

Head Stack Failure Detection and Handling

FIG. 18 illustrates one possible implementation of the present system.From FIG. 18, the media disks of the present system are optionallyencased by a shrouding arrangement, shown as two shrouds, and anacoustic sensor 1801 is mounted on a positioner arm 1802 proximate thedisks. The acoustic sensor is employed to detect the noise produced byone or more heads that come in contact with one or more correspondingdisks upon the occurrence of or in advance of a head crash. When a headcrash is imminent, it is understood that the acoustical emissions by thedrive may take on certain abnormal characteristics, and in the presenceof these abnormal characteristics, it is preferable to remove the heador heads from the disk. Impending head crashes may produce differentcharacteristics in different drives and may even vary under differentcircumstances within a single drive. Unusual or abnormal circumstancesmay include, but are not limited to, high frequency variations orripples. With respect to sensing such abnormal circumstances or theexistence of a head crash, it is to be specifically understood that theacoustic sensor may be located in an alternate position from that shownin FIG. 18, such as on the e-block, on a disk cover, or otherwise, andmore than one such sensor may be employed. Location of the acousticsensor as close to the head as physically possible and practicable isone possible way to locate the sensor. Sensor location will depend on avariety of factors, including but not limited to physical constructionof the servowriter, placement of the heads, and associated acousticalissues.

During normal operation, the head reading from or writing to a disk isdisplaced in physical proximity of the disk. The head and the disk arenormally not in direct physical contact, but are operationally coupled.For example, for a magnetic disk, a head flies relatively close to thesurface of the disk reading from, or writing to the media disk viamagnetic fields that propagate across the physical gap between the headand the disk.

When a head crashes, possibly as a result of a mechanical or powerfailure, the head may contact the corresponding disk producing acharacteristic noise. While a disk failure may create sound waves havingvarying characteristics, the noise is typically characterized byfrequencies and amplitudes in particular ranges. Certain pending headcrashes may also exhibit frequency or amplitude abnormalities. Theimplementation of the invention described herein utilizes an acousticsensor 1801 to detect this characteristic noise. The noisecharacteristic to a head crash exhibits a certain sound intensity andoperates within a certain frequency spectrum. This implementation of theinvention distinguishes the noise characteristic to a head crash fromother noises that may otherwise occur in the system by determining thenoise in the system, detecting amplitude and frequency levels, andindicating when those amplitude and frequency levels fall outside anexpected range or within an undesirable range. The acoustic sensor andassociated electronics only react to sound whose intensity exceeds acertain threshold and whose frequency spectrum matches the frequencyspectrum characteristic to a head crash.

From FIG. 18, media disk 1805 has head 1803 operating above and inassociation therewith. Positioner base 1802 has acoustic sensor 1801affixed thereto, and positioner base 1802 is adjoined to head 1803 viapositioner arm 1804. Acoustic sensor 1801 is electronically linked tocomputing device 1806, which may be any electronic device capable ofdiscriminating between signals, dynamically computing values in realtime, and transmitting command values to a voice coil and/or voice coilmotor, such as a digital signal processor. The computing device 1806determines whether the sound intensity is within an expected range orwithin an unexpected range and commands the VCM (not shown) to lift thehead 1803 from the disk 1805 under failure conditions.

The sound intensity associated with the noise produced by a head crashdepends on various factors, including the physical characteristics ofthe disk and head. The system, via the acoustic sensor 1801 and theassociated electronics, only reacts when the intensity of the sounddetected exceeds a certain threshold or is within an undesirablethreshold range. A value of this threshold may be determinedexperimentally for a particular combination of head and disk, or may bedeveloped analytically. As may be appreciated, a disk failure due to,among other causes, a broken disk, produces a high amplitude sound. Inother circumstances, such as a power failure, a failure is indicated byan absence of sound. Normal operation of disks, particularly inservowriting and certification, is a constant speed rotational sound,sometimes called a “whirring” or “whizzing” sound. These tend to beconstant sounds, unlike a traditional hard drive sound that operates infits and starts depending upon the function performed by the hard diskdrive. In hard disk drive operation, the disk may not spin for a periodof time and then spin for an extended period of time. Theservowriter/certifier hardware system, by contrast, may be either on oroff for an extended period of time, and thus noises outside the expectednorm may be considered a system failure.

In one aspect, the acoustic sensor has a relatively low sensitivity suchthat it only detects noise above the threshold. In another case, theacoustic sensor detects a wider range of sound intensities, but softwareand/or hardware logic coupled to the acoustic sensor responds to thesystem when the sound intensity detected by the sensor is below aparticular threshold. Software and/or hardware logic coupled to theacoustic sensor may be configured to respond to a range of soundthresholds.

The frequency spectrum associated with the noise produced by a headcrash also depends on the physical characteristics of the disk and head,among other factors. The system only reacts when the frequency spectrumof the sound detected matches a certain frequency spectrum signature.This frequency spectrum signature may be determined experimentally for aparticular combination of head and disk or disks, or may be developedanalytically. In one case, the acoustic sensor has a particular spectralsensitivity such that it only detects noise whose frequency spectrummatches the frequency spectrum signature. In another case, the acousticsensor detects a wide range of frequencies, but software and/or hardwarelogic coupled to the acoustic sensor suppresses response of the systemwhen the frequency spectrum detected by the sensor does not match theappropriate frequency spectrum signature. Software and/or hardware logiccoupled to the acoustic sensor, possibly including frequency filteringlogic, may be configured to respond to a range of spectral frequenciesand suppress other frequencies.

The intensity and frequency spectrum of the sound detected by theacoustic sensor may also depend on the proximity of the sensor withrespect to the point of contact between the disk and the head. In aparticular implementation, the acoustic sensor is disposed on the armsupporting the head, in physical proximity to the head. In anotherimplementation, the acoustic sensor is located on the e-block, furtheraway from the head.

In one implementation, multiple acoustic sensors are employed to detecthead crash in a multiple head, multiple disk environment. In thisimplementation, multiple heads read and/or write information to multipledisks substantially simultaneously. There may be more than one headoperationally coupled to each disk. Further, there may be more than onehead coupled to each VCM-driven arm, possibly coupled via actuators, andthere may be more than one arm operating on each disk. In thisimplementation, multiple acoustic sensors may be disposed throughout thesystem to detect head crashes that may occur at any point in the system.Each acoustic sensor and associated logic may correspond to a particularhead and may be configured to ignore head crash noises produced by anyother head. Alternatively, the system may utilize information producedby a multitude of sensors to identify the head that crashed (e.g.,through triangulation and/or through a spectral and intensity soundanalysis that considers the characteristics of various disks, heads andsystem components disposed throughout the system).

If possible, in the current system and in many other systems, theacoustic sensor would be located as close to the head as possible.Physical drive characteristics limit the proximity of the acousticsensor to the disk, but such a sensor may be employed at or near thepositioner, e-block, shroud, or other points in the representativedesign illustrated herein.

In operation, once a head crash or other system failure is detectedusing the sensor or sensors disclosed herein, the system retracts theheads or otherwise moves the head or heads away from the disk or disksas rapidly as possible. This removal of heads from disks providesnecessary space between disk and head. While the head may still contactthe disk under certain failure conditions, such as a disk fracture orhead failure, removal of the heads from the disk breaks the typicalassociation between disks and heads and minimizes the chance of damagingeither. Removing heads from the disk is a normal circumstance of mediaservowriting, and thus the system operates in a known manner whenremoving heads from the disks. Under one condition, a power failurecauses the system to rectify the voltage available from the spindle andthat voltage is applied to the voice coil, or alternately directly tothe voice coil motor, which moves the head or heads away from the mediadisk or disks. In operation, a ramp type structure is moved by the voicecoil motor to contact head holding apparatus and lift the head.

In other words, in one implementation, the invention utilizes thespindle as an electrical power generator to retract the heads off thedisk.

In this implementation, the system utilizes a relay to detect a powerfailure. In one case, the relay detects when the electrical voltage at aparticular point decreases below a certain threshold. In a particularcase, this threshold is eight volts.

Upon a loss of power, the spindle continues to rotate due to its angularmomentum. The mass of the spindle and other subsystems mechanicallycoupled to the spindle is relatively large, such that the angularmomentum of the spindle system is correspondingly large. Upon loss ofpower, the spindle continues to spin for a significant period of time.

The invention exploits the angular momentum of the spindle by utilizingthe spindle as an induction power generator. Inertial rotation of thespindle induces electricity in a coil. This coil may be substantiallystationary with respect to the spindle, and therefore rotate with thespindle, or may be stationary with respect to the base of the spindle.In one case, the coil is part of the electrical motor that engages androtates the spindle under normal operating conditions.

The electrical power produced by the spindle is rectified and isemployed to operate servo systems that may retract the heads off thedisk. In one aspect, the electrical power produced by the spindle isdivided into two components: a first component operates a voice coilmotor that retracts the heads off the disk, while a second componentoperates a motor that moves a ramp that mechanically engages the headsin a preferred resting position.

The present invention may apply to a single head operating on acorresponding disk, to multiple heads operating on a singlecorresponding disk, or to multiple heads operating on multiple disks.

As an alternative to the foregoing, the system may determine that apending crash is imminent or has occurred if vibrations occur within thespindle. In such an arrangement, the spindle is monitored with avibration sensor to detect spindle movement, and abnormal readings infrequency, amplitude, or intensity may be employed to remove the headsfrom the disk in certain circumstances.

This aspect of the invention has been outlined in the context of arotating spindle. In an alternative implementation, the invention mayalso apply to a medium in linear motion (e.g., conveyor belt-type ofsystem). In such a system, failure causes operation of a ramp thatmechanically engages the heads in a preferred resting position.

Media Shroud

1. Multiple-Disk Shroud.

One implementation of the invention disclosed herein provides amultiple-disk shroud comprising a left baffle shroud and a right baffleshroud. From FIG. 19, the left baffle 1901 comprises a plurality ofindividual left baffle cavities 1902 a-n corresponding to disks arrangedin a stacked formation. Each individual left baffle cavity 1902comprises an opening or slot that fits around the media and is adaptedto partially receive a corresponding media disk, thereby partiallyenclosing the disk. In a particular embodiment, each individual leftbaffle cavity 1902 extends substantially to the center of thecorresponding disk, thereby enclosing substantially half of the disk.The distances between the inner planar surfaces of each left baffleshroud and the corresponding planar surfaces of the corresponding diskare preferably small. In a particular case, these distances areapproximately 10 mils, or 10/1000 of one inch. Construction of thisaspect of the current invention therefore comprises a series ofseparating walls, wherein the separating walls create the cavities 1902in the baffle shroud.

As may be appreciated by those skilled in the art, the number of leftbaffle cavities or openings generally corresponds to the number of mediadisks in the arrangement or disk stack, such that the existence of fivedisks in the stack dictates a baffle shroud or shrouds with fivecavities, while the existence of eleven media disks in the stacksuggests eleven left sets of cavities in each baffle shroud. The numberof left baffle cavities is generally related to the number of availabledisks or media that may be employed, rather than the actual numberemployed. In the previous example, if the spindle or disk holding deviceis capable of holding five disks but is only fitted with three disks,the number of cavities will be five. The foregoing is meant by way ofexample and not as a limitation.

The media disks are disposed in substantially parallel planes and mayspin around a common axis that is substantially normal to the planes ofthe media disks. The disks are operationally coupled to correspondingheads that may read and/or write data to the disks.

The left baffle 1901 may be translationally coupled to the frame of theservowriter such that the left baffle 1901 may pivot into physicalproximity of the media disks. In one embodiment, the left baffle 1901 isnot directly coupled to either the media disks or the read/write heads,and may translate independently of the disks and heads. Upon translatingproximally to the disks, each of the individual left baffle shrouds 1902a-n partially encloses a corresponding disk, thereby controlling airflow around the disk as the disk spins at a relatively high velocity.

In a further aspect of the present invention, a right baffle 2001 asillustrated in FIG. 20 is analogous to the left baffle 1901 describedabove and comprises a plurality of individual right baffle cavities 2002a-n corresponding to the number of media disks that may be loaded on thespindle. The structure and functionality of the right baffle aresubstantially the same as the structure and functionality of the leftbaffle, although certain differences exist. One such difference betweenthe left and the right baffles 1901 and 2001 is that the planardimensions of the right baffle shrouds in this aspect of the inventionare smaller, such that each right baffle shroud receives and protects asmaller portion of the corresponding disk. In a particular embodiment,each right baffle shroud encloses substantially a quarter of thecorresponding disk. In a related embodiment, each left baffle shroud andthe corresponding right baffle shroud cooperatively enclose anon-insubstantial portion of the disk, in the aspect illustratedapproximately ¾ of the corresponding disk. The remaining ¼ of each suchdisk is essentially covered by one or more heads and/or other relatedhardware.

Other specific dimensional characteristics are available for the leftand right baffle, as may be appreciated by one of skill in the art. Thefunction and purpose of the shrouding arrangement is to cover as muchmedia disk surface as reasonably practicable while at the same timeallowing reasonably free access by the read and write heads to the mediadisks. Alternate designs include, but are not limited to, use of asingle shroud similar to the left shroud covering approximately half themedia surface, and use of a shroud covering approximately half thesurface similar to the left shroud 1901 and a larger or smallerdimension right shroud than that shown. Dimensions of the shroud orshrouds are dictated by various factors, including desired rotationspeed of the disks, physical dimensions of the positioner arm or arms,amount of media disk access required, and disk holding considerations,such as spindle, chuck, and other holding mechanism dimensions. By wayof example and not limitation, the spacing between the disks and theshroud or baffle hardware may be as small as on the order of 10 mils andpossibly lower, such as 9 or 8 mils.

When engaged in an operational position in the configuration illustratedin FIGS. 19 and 20, the right baffle 2001 may be disposed substantiallyopposite to the left baffle 1901 with respect to the spinning axis ofthe disks. The translating directions of the left and right baffles 1901and 2001 are also opposite, with the left baffle 1901 approaching thedisks from the left direction and the right baffle 2001 approaching thedisks from the right direction. Further, unlike the left baffle 1901,which may translate independently of the heads, the right baffle 2001 ismechanically coupled to the read/write heads and associated positionerin one aspect, such that the heads and the right baffle are disposed onthe same arm. In this aspect, when the heads are engaged in a functionalposition by the voice coil motor (VCM), the right baffle 2001 issubstantially simultaneously disposed in an operational position.Subsequently, during normal operation, the heads may move with respectto the disks and the right baffle 2001 while reading and/or writing tothe disks, but the individual right baffle shrouds 2002 a-n remainsubstantially stationary with respect to the corresponding left baffleshrouds 1902 a-n and the spinning axis of the disks.

It is to be understood that the foregoing represents a single specificdesign of the present invention and is not meant to be limiting to thedesign shown. Translating is not necessarily required, and for examplethe shrouds may be fixed in position, disks may be rotated into theshroud using a movable spindle, and either one, both, or neither shroudmay interact directly with the positioner, VCM, and other systemhardware. The design must, at a minimum, provide a level of coverage orenclosure of the media disks and decrease the risk of windage disruptingthe interaction between head and disk.

In one aspect of the current invention, the left baffle 1901 and theright baffle 2001 are constructed from aluminum. Alternatively, the leftbaffle 1901 and/or the right baffle 2001 may be constructed fromplastic. Other materials may be employed while within the scope of thepresent invention, provided the materials provide adequate strengthcharacteristics and operate to minimize the risk of turbulent flow inthe arrangement selected. Thus materials such as aluminum and/or plasticmay be used, but these materials are neither required nor exclusive forconstructing the inventive baffle arrangement shown herein.

In a particular implementation, the left and/or right baffles 1901and/or 2001 may comprise one or more vacuum ports or inlets (not shownin the illustrated aspect but known to those of skill in the art) thatmay be utilized to remove debris or particles located in proximity ofthe spinning disks. Such debris is typically found in the form of smallparticles, and such small particles may inhibit performance of the diskstack. The inlet operates in connection with a vacuum pump to intake orvacuum air and particles from the shroud arrangement. The inlets may belocated at each baffle, or at one baffle, and may span all chambers ofthe baffle, a single chamber of the baffle, or any intermediate numberof chambers. The purpose and functionality of the inlet arrangement isto remove unwanted particles and provides a means to reduce the quantityof ambient particles contacting disk surfaces in the multi diskarrangement. The inlets or vacuum ports may be a single small diameterhole located atop or on the side of the baffle, or alternately a longsealed opening on the side of the baffle to afford access to each diskand chamber or cavity. Other vacuum port or inlet shapes andconfigurations may be employed while still within the scope of thisaspect of the invention.

While varying dimensions may be employed, particularly of the shroud,baffle, baffle

Alternate views of the baffles are illustrated in FIGS. 22 through 27.FIG. 22 is a top cutaway view of the left baffle. FIG. 23 is a sidecutaway view of the left baffle. FIG. 24 is a bottom view of the leftbaffle. FIG. 25 is a side view of the right baffle. FIG. 26 is analternate perspective view of the right baffle. FIG. 27 is a bottom viewof the right baffle.

2. Clock Head Shroud.

Another embodiment of the invention provides a shroud that may protect amedia disk while a clock head reads or writes data from the disk. Theshroud of this aspect of the invention is presented in FIG. 28. Theclock shroud 2801 encloses the head at close proximity to the disksubstantially completely, but comprises a number of apertures, such asfirst relief cut 2802 and second relief cut 2803, that permitintroduction and withdrawal of the clock head and/or of other devices.Such relief cuts are beneficial in certain circumstances but are notrequired as part of the present invention; rather, the important aspectof the invention is to provide a shroud or covering that covers the headand decreases the amount of windage encountering the head and reducesrisk of disruption of the head-media disk interaction. In the designshown, additional apertures located in the shroud permit disposition ofcertain devices, such as a motor. The use of the clock shroud enables amore accurate clock and timing arrangement for the system, minimizesinterference between the clock head and the disk, keeps certain data,such as servo pattern data phase coherent, and minimizes vibration. Theclock head sits in the notch illustrated in FIG. 28. FIG. 29 is a topview of a clock shroud that may be employed in association with thecurrent invention.

Head Mounting Design

A further aspect of the present design is employed in connection withthe heads writing to and reading from the media in the configurationpresented above. More particularly, the present design includes a systemand method for mounting the heads to relevant hardware, such as anassembly or holding device, positioner arms and an E-block, so that theheads can be removed and replaced in a more efficient manner thanpreviously known.

FIG. 30 presents one rotary voice coil motor design 3001 that may beemployed in a media track writer or servowriter as shown above, whereinthe voice coil motor is used to drive the head positioner and the headslocated thereon. The voice coil motor design 3001 is a balanced torquedesign having twin coils 3002 and 3003 placed on opposite sides of acentral pivot. The rotating portion of the voice coil motor is suspendedon two high precision preloaded ball bearings (not shown), and includesthe coil housing 3101 of FIG. 31, two coils 3201 shown in FIG. 32, scaleholder 3301 and shaft 3302. The shaft on the scale holder 3301 and shaft3302 assembly, including dowels 3303, 3304, and 3305, are used to guideand align the scale holder to the FIG. 34 E-block positioner armassembly 3401. The shaft 3302 fits into cavity 3402 in E-blockpositioner arm assembly 3401, with coarse angular alignment establishedby crosswise dowel pin 3303 and final angular alignment performed bysmaller dowel pin 3304. E-Block 3403 is attached to the remainder of theE-Block positioner arm assembly 3401. This smaller dowel pin 3304 isinserted between scale holder 3301 and the E-block positioner armassembly 3401. A standard wing nut, not shown, fastens the E-blockpositioner arm assembly 3401 to the scale holder 3301 and shaft 3302.This wing-nut attachment of E-block and head assembly provides for rapidloosening of the wing nut, releasing the shaft, removing the shaft, anddisengaging the E-Block positioner arm assembly 3401 from the rest ofthe media writer. It is desirable to periodically replace the headassembly to address normal wear and tear during servowriting or damageto one or more heads resulting from faulty disks while retaining theassembly for future use.

With respect to the head assembly, and namely the assembly exclusive ofthe head, E-Block, and positioner arms, the way the device is assembledduring operation is as follows. Individual head-gimbal assemblies (HGAs)are attached to small mounting tabs. When assembled, the HGA may beattached to mounting tab 3501 as shown in FIG. 35, which is then affixedto the arms of the E-block 3601, shown in detail in FIG. 36. Eachmounting tab 3501 is held in place on the E-block arms using a smallscrew, such as a M1.2 screw, which passes through channel 3504. FIG. 36illustrates a top view of the E-Block 3601 bifurcated by an imaginarycenterline. Alignment of the mounting tab and E-block 3601 of FIG. 36occurs using the two dowel pointed pins 3502 and 3503, which areultimately inserted into two slots 3602 and 3603 in E-Block 3601. Fromthe angle of FIG. 36, only one slot 3603 is visible. Use of the dowelpointed pins 3502 and 3503 align the tab 3501 to the arm 3606 of theE-block 3601. A tab having one or two heads may be removed from orassembled to the E-block with the installation or removal of a singlescrew.

The present apparatus obviates the need for the previous method of“staking.” The present design uses a press fit scheme, whereby the HGAand head mount components are pressed into place and secured to otherassemblies using dowels, pins, screw, wing nut, and other components.Staking required mounting tab replacement or head arm or E-block afteronly two or three head replacements due to permanent deformation of theboss receiving bore 3504 of the head mount. The present design employs asmaller head bore 3504 than the mating boss on the head suspension,enabling the HGA to be attached to the head mount by applying pressure,or pressing, the part and forcing the suspension boss into the headmount bore 3504. This pressing operation allows the suspension boss tomaintain sufficient torque to allow proper head operation duringfunctions such as ramp load and unload of heads onto the disks. Comparedto staking, a press fit or a pressure fitting has the ability to impartless distortion to the interface between the HGA and the mating headmount bore, increasing the number of reuses of the head mount tab 3501before replacement is indicated. Since HGA distortion is generally lessthan that of the mating head mount bore, head damage can be minimized bypress fitting rather than staking.

An alignment and pressing fixture may be employed to assemble one or twoHGAs to a head mount. HGAs may be assembled using the devices shown inFIG. 37. In practice, the head mount is located within the centersection 3702 while one or two HGAs are affixed to the head mountdepending on the application. HGAs are sandwiched between the leftsection 3701 and the head mount fixedly positioned within center section3702, and/or the head mount fixedly positioned within the center section3702 and the right section 3703. The heads are then aligned with andaffixed to the head mount tab, which is thereafter assembled on theE-block.

FIG. 37 illustrates an exploded view of the three sections and theassociated hardware used to prepare the HGA or head assembly and mountfor receiving a read/write head. In FIG. 37, the head mount tab (notshown) is mounted to the head assembly tool 3704. The center section isused to align and mount the tab to the HGA using the aforementioned M1.2screw (not shown in this Figure). Heads are placed between the press-fitjaws of left and right assembly tool parts 3701 and 3703, between thoseassembly tool parts and the center section 3702, and are aligned usingthe HGA support 3705. The right head assembly tool part 3701 may beforced toward the center section 3702 using a vise or other clampingdevice, and the HGA bosses are press fit to the head mount tab bore. Thehead mount tab is aligned using the HGA support 3705 and alignment toolpins 3706 and 3707. The pins may be a straight or stepped pin to providenecessary support and alignment for the tasks outlined below.

Each of the assembly tool parts, left section 3701, center section 3702,and right section 3703 have slots cut through the material to providelimited lateral flexibility. The flexibility enables the tool to be usedfor a head to be assembled on either side of the head mount tab, or bothsides may be assembled at once.

FIGS. 38A, 38B, and 384C show details of the three assembly tool parts,left section 3701, center section 3702, and right section 3703. Theseare representative of one possible implementation, and otherimplementations may be employed while within the scope of the presentinvention.

Assembly of the system is shown in FIGS. 39-43. FIG. 39 illustrates ahigh precision vise 3901, the two alignment tool pins 3706 and 3707, theassembly tool 3902 comprising left section 3702, center section 3703,and right section 3704, the head assembly 3803, and tools for performingthe head assembly. ESD protection may be employed during handlingoperation, and the work may be performed under a clean hood by anoperator with gloved hands. The assembly tool may be constructed fromany appropriate material, including but not limited to stainless steel,such as a cold rolled type 302 or 304 stainless steel. Other materialsmay be employed that provide sufficient holding, wear, and strengthcharacteristics, among other advantageous aspects.

Head arm mount 3501 is inserted into the assembly tool 3902. The headassembly tool 3902 is maintained within the precision vise 3901 graspingthe base of the tool 3902, thereby applying a level of pressure ortension to the assembly tool, but not so much as to restrict movement ofthe upper section of the tool sections. The center, right, and leftsections of the assembly tool 3905 may be spread such that the head armmount may be inserted in the gap and the pins of the head arm mountaligned into the center section 3703 of the assembly tool 3902.Spreading may occur by various means, including using the operator'sfingers to separate the left, center, and right sections of the assemblytool 3902. The M1.2 screw is then tightened, thereby wedging the sidesof the head arm mount 3501 within the center section 3703 of theassembly tool 3905. The operator or a machine may then pick up the headassembly, spread the outer members of the assembly tool and gentlyinsert the head assembly between two of the sections, such as the leftsection 3702 and the head arm mount 3501. The staking boss (not shown)of the head assembly 3903 may be approximately aligned with the upperhole of the head arm mount 3501.

FIG. 40 presents a side view of a sample head assembly 3903, held withtweezers by an operator. This sample head assembly is onlyrepresentative of the types of head assemblies that may be employed, andthe head assembly shown has the ability to maintain the drive head 4002at the top end in the orientation shown and has various openings whichenable the assembly and alignment described below. It is to beparticularly noted that other head assembly designs may be employedwhile still within the scope of the present invention.

In initial operation, the head arm mount 3501 is located within theassembly tool 3905, namely center section 3702. In an orientation wherethe center section spacing gap is positioned upward, the pins 3502 and3503 of the head arm mount 3501 are oriented downward and the head armmount 3501 is pushed down into the center section 3702. A screw isinserted through channel 3504, such as an M1.2 screw, to apply pressureto the sides of the head arm mount 3501 and fixedly mount the head armmount 3501 to the center section 3702. FIG. 41 illustrates a head armmount 3501 positioned against the head assembly 3903 within the assemblytool 3905. FIG. 41 further illustrates insertion of a pin 3707, such asa straight 0.8 mm diameter pin, through the upper slots of the assemblytool 4103 and through a tooling pin hole in the head assembly 4103.

In certain circumstances, the head assembly may be repositioned so thatpin 3707 can engage the tooling hole in the head assembly 3903. FIG. 42illustrates insertion of pin 3706, such as a stepped 2.13 mm diameterpin, into a lower hole 4201 in the assembly tool 3905. The pin 3706 maybe inserted carefully such that it passes through the head assembly3903. An operator or machine may at this point inspect alignment of thehead assembly 3903 within the head arm mount 3904. Inspection may occurin any available reasonable manner, including but not limited to a lowpower stereo inspection microscope. If alignment is acceptable, the pins3706 and 3707 may be removed from the alignment tool. Spring pressurefrom the assembly tool 3905 in many circumstances will keep the headassembly aligned to the head arm mount 3501.

The upper edge of the alignment tool 3905 may then be repositionedwithin the vise 3901 as shown in FIG. 43. A relatively small section ofthe alignment tool 3905 may be inserted into the vise 3901, such as lessthan 10 mm. A relatively small amount of pressure is then applied bytightening the vise 3901, thereby press fitting the head assembly 3903into the head arm mount 3904. The screw may then be removed from thehead arm mount 3501 and the head assembly press fitted to the head armmount 3501 may be removed from the assembly tool.

Other implementations of the press fitting method described above arewithin the scope of the present invention, and the foregoingdescription, as with all descriptions of particular design aspectsherein, is not intended to be restrictive or limiting.

Disk Biasing

An aspect of the present invention provides methods and systems forcontrolling disk position on a central hub or chuck during servo trackwriting and/or reading. The disk position control may occur prior toinstallation into a Hard Disk Drive. The disk biasing methods andsystems disclosed herein may be applied to single or multiple disks,require minimal or no operator intervention, and provide a repeatableway to control eccentric placement of servo information onto the disk.

One aspect of the MTW that is particularly noteworthy is the mechanicalclearance between the disk inside diameter, and the hub or chuck outsidediameter, namely the disk opening and the hub that fills the opening. Asignificant clearance dimension is necessary to enable fast and reliabledisk installation on and off the hub and to accommodate disk and hubmanufacturing tolerances. Excessive eccentricity, or servo track“runout”, can cause servo capture and performance problems for the HDD,in that the head can be mislocated above the disk and can run outside atrack, or begin in one track and end in another.

One way to deal with this excessive eccentricity aspect of a media trackwriter is to have a mechanism to “center” the disk on the hub at diskinstallation. Centering the disk typically may require precise andexpensive fixturing to achieve reasonable accuracy. Another, often lessexpensive, way to address excessive concentricity is to “bias” the diskID against the hub OD in a controlled manner so that this same “bias”can be applied when the disk is eventually installed into an HDA,thereby controlling the eccentricity rather than allowing tolerances tovary unpredictably to significant error levels. A necessary part of thisprocess is maintaining and/or determining the bias direction andcircumferential point where the bias is applied. Such use of biasdirection and circumferential point may be accomplished by marking thedisks or by handling the disks in a controlled and repeatable way.

To consistently bias a disk, an embodiment of the invention can applybiasing force to the disk OD, usually by using a very precise fixture ortool. By alternately biasing disks against the HDA spindle hub inopposite directions using “V” shape devices to push on the disk OD,rotational unbalance forces can be minimized. Typically, these “V” shapedevices are placed on either side of the disk and spindle stack, suchthat half the disks are biased in one direction and the other halfbiased 180 degrees in the opposite direction. This way, for stacks ofeven numbers of disks, first order disk unbalances can be minimized.These “V” shape blades may be made slightly compliant to compensate fordisk, spindle hub, and biasing tool mechanical tolerances, either byusing a compliant material or some mechanical compliance, such as aspring type mechanism. The vertical axis of the biasing tool used toapply the “V” shape blades may be precisely aligned to the spindle hubaxis to consistently bias the disks in the appropriate direction at alllocations in the disk stack. Further, biasing of disk spacers may beemployed using OD biasing.

An embodiment of the invention biases the disks using the disk ID. Inthis case, biasing forces are applied in an outward radial direction tothe disk ID at one or more points, such as two points, to force the diskin a known direction against the spindle hub. The biasing force can beapplied in various ways, including but not limited to using air pressureto automatically bias disks in the stack in the required direction. Two,small, piston-like devices within the spindle hub may be used to apply aradial vector sum force in a known direction to each disk. By arrangingthe piston-like devices in a pattern, forces can be directed in anydirection for each disk. The simplest pattern would be 180 degreeopposite force vectors for each disk, such that the net rotationalunbalance force for an even number of disks, assuming identical disks,would be zero. Even numbers of disks ensure dynamic as well as staticforce balance. For each disk, each group of two piston-like devices isarranged in a manner to provide a vector sum force in a known direction.

According to an embodiment, an arrangement that facilitates themanufacturing process, comprises two pistons radially oriented withrespect to hub axis and spaced an angle apart. Although many angles willwork, the preferred angle for manufacturing is 90 degrees. This angleprovides a vector sum of 1.414 times the force generated by each piston,in a direction half-way between the pistons, or in this case, 45 degreesfrom either piston, directed radially outward. In addition, lateralforces are generated by each piston, and these lateral forces tend toforce the disk laterally until a force balance exists on the disk.Friction related forces may also exist. A friction force has a tendencyto oppose the biasing force, irrespective of the direction of thebiasing force.

The directional accuracy with which the disk will be biased depends uponthe ratio of the magnitudes of the friction force to the biasing force.It may be beneficial in certain circumstances to minimize friction andmaximize the biasing forces for each disk. Friction between disks anddisk spacers can be minimized by using special plating processes on thespacers. For example, hard nickel plating or nickel plating withembedded Teflon particles have demonstrated low friction coefficientswith most disk surfaces. Other coatings and/or materials can be used aswell.

One implementation of the present aspect of the design includes a fourdisk chuck assembly with integral disk biasing. Disks are stacked onto achuck and spaced vertically using a spacer. Once the stack is assembledand biasing done, the stack is clamped together using a top cap. Biasingis accomplished by use of pressurized air or other gas such as nitrogen,prior to clamping. Disk clamping is performed with a single screw,although alternate designs may utilize vacuum or other mechanicalclamping means. Air or other gas used for biasing is introduced throughthe bottom base of chuck, distributed by a shaft, with biasing forcesgenerated by a ball and orifice housing assembly. If both air pressureand vacuum is used (first for biasing then for clamping), internal checkvalves within chuck body direct air or vacuum to the appropriate areasas necessary. The biasing forces generated by the pair of ball andorifice housing assemblies are self balancing via use of a seriescombination fixed and variable orifice within the assembly.

The design resembles air-bearing systems where self balancing forces aregenerated by use of a fixed orifice in series with a variable orifice,with the air pressure between the two orifices used to provide a liftingor noncontact bearing action. In an air bearing, the variable orifice isnearly always created by one member of the bearing moving with respectto the other. In this biasing design, the variable orifice is createdbetween the moving ball which contacts the disk I.D. and the angled ballseat within the housing. Pressurized air flows first through the fixedorifice, which is in the order of 0.010 inches diameter, then throughthe variable orifice. The air pressure between the 2 orifices acts onthe ball to create a force directly proportional to that pressure. Asthe ball moves outward, the pressure falls, reducing ball force. As theball moves inward, thus reducing the area of the variable orifice, thepressure increases, increasing the ball force. With two of these balland orifice housing assemblies arranged so that radially outward forcesare applied to a disk at a fixed angle between the devices, a vector sumforce can be applied such that the direction is controlled. Use of thefixed/variable orifice set devices provides a self-balancing action suchthat the force vector always applies a force vector to the disk suchthat the disk is forced or “biased” against the chuck body in a specificdirection and point on the chuck. That contact point between disk andhub is approximately 180 degrees opposite the two ball orifice housingpiston devices.

By alternating the direction, e.g. 180 degrees, in sequence for eachdisk, the disks can be forced outward in alternating directions suchthat half the disks are biased one way and half are biased the oppositedirection. This alternating of bias direction compensates forfirst-order unbalance effects due to the disk centers being displacedfrom the chuck rotational center.

The described disk ID “biasing” method is but one of many possibledetail configurations wherein changes in the design would not provide afundamental difference from the basic concept described herein.Specifically, the number of disks, disk spacing and angles between thepair of ball and orifice housings can be easily modified to a nearinfinite number of combinations without affecting the fundamentaloperation of the biasing concept. Also, the pushing elements can beother than ball shapes, including but not limited to other piston-likedevices. In addition, while a fixed orifice in combination with variableorifice is believed to have higher accuracy of final vector direction,it may also be possible to simplify the design further, by using pistonsor balls alone within a simple radial bore, provided the forces arelimited so that no permanent disk ID surface deformation, “brinneling”,or other damage occur.

Locking Cap

A further aspect of the present invention includes a specific mechanicalaspect used to hold one or more of the disks in place in the mediaservowriter. An aspect of the present system includes certain aspectsdesigned to facilitate maintaining disks at high rotation speeds. FIG.44 illustrates a general view of one aspect of the device. FIG. 44illustrates the disk maintenance design in a locked down configuration.A closer view of the inner elements of the design is presented in FIG.45. The device includes a top cap 4401, a central chamber 4402, anannular compression spring 4403 and 4404 designed to pull the capdownward, and a set of ball bearings 4405, two of which are visible inthese views, abutting the central core 4406 of the cap 4401. To unlockthe device, the cap 4401 must be released, which requires application ofair to the central chamber. Air is applied to the central chamberthrough the bottom of the device (hub). Air pushes up the centralcylinder and the ball bearings 4405 buttressing the central core 4406 ofthe cap, thereby applying tension to the compression springs 4403 and4404. When the ball bearings 4405 and the chambers in which they arelocated rise to a level proximate the upward sloping walls in theinterior of the chamber, the ball bearings 4405 slide outward along theupward sloping walls 4407 and out of the way of the central core 4406 ofthe cap 4401. With the ball bearings 4405 out of the way, the cap 4401can be readily released and disks 4410 either loaded or unloaded. Inlieu of using air to engage and release the mechanism and cap 4401, apushrod 4410 may be employed to push the central core upward and releasethe cap.

FIGS. 46 and 47 illustrate the cap in released position with the ballbearing and cap core in released position. Application of the cap 4401,specifically locking the cap down, requires removing air pressure fromthe interior of the cap, whereupon the central chamber slides downwardand the ball bearings re-seat in the sloping holes and lock down thecap. Most of the components illustrated in these drawings are fashionedof metal, while the cap may be fashioned of a hardened plastic. Anymaterials may be employed that satisfy the engagement and releaseaspects and functionality described herein, and the central core andother exterior components, for example, may be fashioned of steel,nickel, or any other strong metal.

FIGS. 46 and 47 illustrate the ball bearings 4405 after having risen upto meet the chamber inner walls. The second figure is a close up view ofthe first figure. FIGS. 46 and 47 represent an alternative constructhaving larger compression springs and a larger interior chamber. Thepresent design uses six ball bearings with six inner conical-shapedpassages in the ball bearing set 4405. More or fewer ball bearings maybe used. Alternate sloping of the channels where the ball bearings sitor the inner chamber walls which receive the ball bearings may beemployed, as long as depressurization causes a release of the cap andpressurization holds the cap in place.

The present aspect of the system may be employed in a hard disk driveemploying multiple disks, such as a servowriter and/or certificationsystem verifying multiple disks, or in any other application requiringuse of multiple fixed media, such as computer disks.

Multiple Finger Clamp

An additional aspect of the present system provides systems and methodsfor holding a hub, specifically a hub of a disk stacking cylinderemployed to hold multiple disks during disk servowriting andcertification. Previously available hub holding devices used some typeof mechanical “jaws” that gripped the exterior of the hub and/or thenotch formed between the hub and the main cylinder. The jaws were formedof some type of metal and were metal pieces used to pin the hub down andhold it in position by applying pressure to the upper side of the hub.These jaw-type locking devices tend to be imprecise in holding the hubor other cylindrical piece. At significantly high RPMs, such as inexcess of 10,000 to 20,000 RPMs, centrifugal force works to pry thesedevices open, and many jaw type devices are pried open or move the pieceas a result of high forces applied thereto. This prying tends to damagethe hub and/or maintaining device and is generally unacceptable. Thusthe previous devices could be characterized as easily pried open, withpoor repeatability, and highly subject to movement of the piece.

FIG. 48 illustrates one aspect of the present design. The lowest pieceis the spindle 4801, to which the chuck mounting plate 4802 is bolted.The central piece of the chuck mounting plate 4802 is the spindle 4803.The piece surrounding the chuck mounting plate 4802 and engaging the hub4804 is the chuck clamp 4805. This design is air-actuated by passing airupward through the spindle and around the chuck mounting plate 4802.When air is applied, such as at a pressure of 60 psi, the chuck clamp4805 rises and the hub 4804 can be removed from the clamp due to the setof fingers 4806 at the top of the clamp 4805, releasing the grip on thehub 4804. When air is applied, the Bellville spring 4807 collapses, andthe central chuck clamp 4805 rises upward in the orientation shown, andreleases. The “fingers” 4806 on the exterior flex and permit a closegrip under ambient conditions. In other words, when the machine fails,it defaults to the gripped position shown in FIG. 48. The circles in thecentral chuck clamp are O-rings 4808 that provide air seals when inoperation. The application of air pressure and the upward releasing pushwith the finger configuration shown enables sufficient clearance to“grasp” the hub 4804. The design shown has good positionalrepeatability, and the fail-safe design offers advantages over existingdesigns.

All parts may be fabricated from steel or similar material providing thefunctionality described, while the fingers 4806 and associated chuckclamp 4805 may be formed from high strength aluminum. This materialaffords sufficient flexibility of the fingers in the configuration shownwhile at the same time providing sufficient strength to hold the hub4804. The fingers 4806 and aluminum chuck clamp 4805 may be coated witha synergistic coating that provides significant lubrisity. The chuckclamp housing may be formed from hardened steel. Again, other materialsmay be used as long as they provide the functionality and benefitsdescribed herein.

Further illustrations of the present design are shown in FIGS. 49 and50. The angles of the fingers 4806 may be altered from the currentapproximate 10 degrees shown in FIG. 45 to 5 degrees or some othernumber. Further, the present design uses six fingers, but any numbergreater than three fingers could be used with likely adequate results.The present aspect of the design may be employed in any spin devicewhere a hub or rounded end piece must be grasped accurately, such as alathe or other industrial application. The implementation illustratedherein is that of clamping a disk hub for use in servowriting and diskinspection.

While the invention has been described in connection with specificembodiments thereof, it will be understood that the invention is capableof further modifications. This application is intended to cover anyvariations, uses or adaptations of the invention following, in general,the principles of the invention, and including such departures from thepresent disclosure as come within known and customary practice withinthe art to which the invention pertains.

1. A method for tracking and controlling media read/writecharacteristics, comprising: creating media having a predeterminedexpected baseline configuration; reading said media having thepredetermined expected baseline configuration; determining whether saidmedia has moved from an expected position based on the media reading ofthe predetermined expected baseline condition; and correcting datahardware based on determining whether said media has moved from saidexpected position.
 2. The method of claim 1, wherein said predeterminedbaseline configuration comprises media organization structure.
 3. Themethod of claim 2, wherein media organization structure comprises datatrack structure and said media is a computer hard disk.
 4. The method ofclaim 2, wherein media organization structure comprises servo data trackstructure and said media is a computer hard disk.
 5. The method of claim1, wherein said determining comprises utilizing a non-contact radiationdetection system interacting with the media to detect alterations in thepredetermined expected baseline configuration and hardware coupled tosaid media.
 6. The method of claim 1, said media having two sides,wherein said reading comprises reading more than one side of the media.7. The method of claim 1, wherein said correcting comprises determiningdeviations in media position based on the predetermined expectedbaseline condition and moving data hardware to align said data hardwarewith the media.
 8. A method for dynamically tracking and controllingerrors in media operation, comprising: producing an ideal disk usingpatterning technology; and utilizing a non-contact radiation detectionsystem with said ideal disk to detect media movement; wherein data fromthe media is fed back to hardware and/or software to compensate forposition errors during reading and/or writing to the media.
 9. Themethod of claim 8, wherein producing the ideal disk comprises producinga disk having data track structure information located thereon.
 10. Themethod of claim 9, wherein producing the ideal disk comprises usinglithography methods.
 11. The method of claim 9, wherein producing theideal disk comprises writing tracks using at least one electron beam.12. The method of claim 9, wherein producing the ideal disk comprisesproviding the ideal disk with a media organization structure.
 13. Themethod of claim 12, wherein media organization structure comprises datatrack structure.
 14. The method of claim 12, wherein media organizationstructure comprises servo data track structure.
 15. The method of claim9, wherein said utilizing comprises interacting with the ideal disk todetect alterations in the patterning technology and hardware coupled tosaid ideal disk.
 16. The method of claim 9, said ideal disk having twosides, wherein said utilizing comprises reading from the two sides ofthe ideal disk.
 17. A method of dynamically tracking and controllingerrors in media operation, comprising: creating an ideal magnetic diskto detect media movement; placing said ideal magnetic disk inassociation with at least one other media; monitoring said idealmagnetic disk for electromagnetic variations in media position; andcorrecting hardware positioning based on said monitoring results. 18.The method of claim 17, wherein creating the ideal disk comprisesproducing an ideal disk having disk track structure information locatedthereon.
 19. The method of claim 17, wherein creating the ideal diskcomprises using lithography methods.
 20. The method of claim 17, whereincreating the ideal disk comprises writing tracks using at least oneelectron beam.
 21. The method of claim 17, wherein creating the idealdisk comprises providing the ideal disk with a media organizationstructure.
 22. The method of claim 17, wherein media organizationstructure comprises data track structure.
 23. The method of claim 17,wherein media organization structure comprises servo data trackstructure.
 24. The method of claim 17, wherein said monitoring comprisesemploying non-contact methods to detect alterations in the patterningtechnology and hardware coupled to the ideal disk.
 25. The method ofclaim 17, said ideal disk having two sides, wherein said monitoringcomprises reading from the two sides of the ideal disk.
 26. In a systemfor writing to at least one magnetic disk, the system comprising atleast one head, a method for interfacing with at least one magnetic diskcomprising: creating at least one reference medium comprising referencedata; reading reference data from the at least one reference mediumusing at least one head; determining relative movement between thereference medium and the head using reference data received from saidreading; and reducing relative movement in response to a determinationof relative movement between the reference medium and the head.
 27. Themethod of claim 26, wherein said interfacing comprises reading from theat least one magnetic disk.
 28. The method of claim 26, wherein saidinterfacing comprises writing to the at least one magnetic disk.
 29. Themethod of claim 26, wherein creating comprises making a referencemagnetic disk and reading reference data comprises reading magneticreference data.
 30. The method of claim 26, wherein creating comprisesproducing a disk using one from a group comprising: patterningtechnology; lithography; and writing using an electron beam.
 31. Themethod of claim 30, wherein reading comprises one from the groupcomprising: reflecting light energy from the disk; refracting lightenergy; and transmitting light energy.
 32. The method of claim 26,wherein reducing relative movement comprises moving the spindle.
 33. Themethod of claim 26, wherein reducing relative movement comprises movingthe head.
 34. The method of claim 32, wherein moving the spindlecomprises one from a group comprising: using an air pulse to alterspindle position; utilizing a mechanical centrifugal device; varying aninternal magnetic field within an electromotor associated with thespindle; and varying an external magnetic field surrounding the spindle.35. The method of claim 33, wherein moving the head comprises one fromthe group comprising: moving a tip of an arm attached to the head,wherein each arm is jointed and has an individual actuator associatedtherewith; and moving an arm attached to the head.
 36. A method ofdynamically tracking and controlling errors on media disks, comprising:forming an ideal disk having predetermined characteristics locatedthereon; and operating said ideal disk in association with at least onemedia disk; wherein said operating comprises determining whether said atleast one media disk has moved from an expected position based onreading the ideal disk and the predetermined characteristics thereon.37. The method of claim 36, wherein said predetermined characteristicscomprise media organization structure.
 38. The method of claim 37,wherein media organization structure comprises data track structure andsaid media disks are computer hard disks.
 39. The method of claim 37,wherein media organization structure comprises servo data trackstructure and said media disks are computer hard disks.
 40. The methodof claim 36, wherein said operating comprises utilizing a non-contactradiation detection system interacting with the media to detectalterations in the predetermined characteristics and hardware coupled toat least one media disk.
 41. The method of claim 36, said ideal diskhaving two sides, wherein said operating comprises reading more than oneside of the ideal disk.
 42. The method of claim 36, further comprisingcorrecting for perceived errors, wherein said correcting comprisesdetermining deviations in media disk position based on the predeterminedexpected baseline condition and moving data hardware to align said datahardware with the media disk.
 43. A method for minimizing likelihood ofa head within a servowriting apparatus contacting a disk locatedtherein, comprising: sensing sound intensity in a predeterminedfrequency range from a first sensor positioned at a first locationwithin the servowriting apparatus; determining the existence of apending head crash based on the sound intensity; and moving an elementof the servowriting apparatus upon determining the existence of thepending head crash.
 44. The method of claim 43, wherein moving theelement causes the head to move away from the disk.
 45. The method ofclaim 43, further comprising: additionally sensing sound intensity froma second sensor positioned at a second position within the servowritingapparatus.
 46. A method of preserving disk integrity in a mediaservowriter, comprising: receiving acoustic signals; identifyingacoustic signals falling within a predetermined range; assessing theprobability signals within the predetermined range constitute a likelyfailure event; and retracting equipment within the servowriter toprevent contact between devices within the servowriter and the disk. 47.The method of claim 46, wherein said receiving acoustic signalscomprises receiving signals at a plurality of locations within the mediaservowriter.
 48. The method of claim 46, wherein said retractingequipment causes a head to move away from a disk located within themedia servowriter.
 49. The method of claim 46, wherein assessingcomprises determining whether at least one from a group of attributes isoutside a predetermined boundary, the group of attributes comprising:amplitude; frequency; and intensity.
 50. An apparatus for decreasinglikelihood of a head contacting a disk in a servowriting system,comprising: a sensor capable of detecting a presence of sound intensityat a predetermined intensity range; a computing device programmed todetermine the presence of an undesired event; and retraction apparatusfor retracting said head from said disk when the computing devicedetermines the presence of the undesired event.
 51. The system of claim50, further comprising at least one additional listening device fordetecting a presence of sound intensity at a plurality of points withinthe system.
 52. The system of claim 50, wherein the undesired eventcomprises an impending head crash.
 53. The system of claim 50, whereinthe undesired event comprises a head crash.
 54. A method of preservingdisk and head integrity in a media servowriter, comprising: receivingsound signals falling within a certain intensity range; determiningwhether the sound signals may constitute a failure event; and retractingthe head away from the disk when the sound signals are determined toconstitute the failure event.
 55. The system of claim 54, wherein saidreceiving comprises detecting a presence of sound intensity at aplurality of points within the media servowriter.
 56. The system ofclaim 50, wherein the failure event comprises an impending head crash.57. The system of claim 50, wherein the failure event comprises a headcrash.
 58. An apparatus for determining failure in connection with aservowriting system, comprising: means for detecting sounds made by theservowriting system; and means for determining whether detected soundsconstitute a servowriting system failure.
 59. The apparatus of claim 58,wherein said detecting means comprise an acoustical sensor.
 60. Theapparatus of claim 59, wherein the detecting means further comprise anadditional acoustical sensor positioned remotely from the acousticalsensor.
 61. The apparatus of claim 58, wherein said determining meansdetermine the presence of an impending head crash.
 62. The apparatus ofclaim 58, wherein said determining means determine the existence of ahead crash.
 63. The apparatus of claim 58, wherein the determining meansmonitor at least one characteristic from a group comprising amplitude,frequency, and intensity of the sounds, and wherein the determiningmeans determines the servowriting system failure when the monitoredcharacteristic performs outside a predetermined expected value.
 64. Anapparatus for controlling airflow over rotating media, comprising: atleast one baffle covering the media, the at least one baffle comprisingat least one cavity shielding at least a portion of the rotating media;wherein the at least one baffle provides the ability to inhibitturbulent flow when the rotating media rotates.
 65. The apparatus ofclaim 64, wherein the apparatus operates and rotating media rotates inthe presence of a pressure reduced from atmospheric pressure.
 66. Theapparatus of claim 64, wherein the apparatus operates and rotating mediarotates in the presence of vacuum conditions.
 67. The apparatus of claim64, further comprising a second baffle covering the rotating media,wherein the two baffles shield substantially all of the rotating mediasave for mechanical components interacting with the rotating media. 68.The apparatus of claim 67, wherein each baffle contains a plurality ofcavities, the plurality of cavities corresponding to the quantity ofrotating media able to be placed in the apparatus.
 69. The apparatus ofclaim 64, further comprising media access equipment and a second baffle,wherein said baffle, said second baffle, and said media access equipmentsubstantially shield the rotating media.
 70. An apparatus forcontrolling airflow over rotating media, said rotating media associatedwith a head positioner, comprising: a baffle arrangement shielding anon-insubstantial of the rotating media formed such that head positionerhardware has access to a non-insubstantial portion of the rotatingmedia, said baffle arrangement comprising at least one baffle havingopenings formed to enclose individual rotating media therein.
 71. Theapparatus of claim 70, wherein the apparatus operates and rotating mediarotates in the presence of a pressure reduced from atmospheric pressure.72. The apparatus of claim 70, wherein the apparatus operates androtating media rotates in the presence of vacuum conditions.
 73. Theapparatus of claim 70, wherein the baffle arrangement further comprisesa second baffle covering the rotating media, wherein the two bafflesshield substantially all of the rotating media save for the headpositioner hardware interacting with the rotating media.
 74. Theapparatus of claim 73, wherein each baffle contains a plurality ofcavities, the plurality of cavities corresponding to the quantity ofrotating media able to be placed in the apparatus.
 75. An apparatus forcontrolling airflow over rotating media, said rotating mediaintermittently being in contact with at least one head, said at leastone head being associated with head maintaining hardware, comprising: ashroud having at least one relief cut for holding the at least one headand the head maintaining hardware over the rotating media, wherein theshroud tends to decrease airflow contacting the at least one head. 76.The apparatus of claim 75, wherein the apparatus operates and rotatingmedia rotates in the presence of a pressure reduced from atmosphericpressure.
 77. The apparatus of claim 75, wherein the apparatus operatesand rotating media rotates in the presence of vacuum conditions.
 78. Theapparatus of claim 75, further comprising a second shroud covering therotating media, wherein the two shrouds shield substantially all of therotating media save for the head maintaining hardware interacting withthe rotating media.
 79. The apparatus of claim 78, wherein each shroudcontains a plurality of cavities.
 80. The apparatus of claim 75, furthercomprising an additional shroud, wherein the two shrouds cover the atleast one head while allowing for free operation of head maintaininghardware and simultaneously enable reduced airflow over the rotatingmedia.
 81. An apparatus for controlling airflow over rotating media,comprising: a plurality of baffles covering the rotating media, eachbaffle comprising: a plurality of cavities, each cavity covering atleast a portion of a subset of the rotating media, wherein the baffleand plurality of shrouds tend to inhibit turbulent airflow duringrotation of the rotating media.
 82. The apparatus of claim 81, whereinthe apparatus operates and rotating media rotates in the presence of apressure reduced from atmospheric pressure.
 83. The apparatus of claim81, wherein the apparatus operates and rotating media rotates in thepresence of vacuum conditions.
 84. The apparatus of claim 81, saidplurality of baffles comprising two baffles, wherein the two bafflesshield substantially all of the rotating media save for mechanicalcomponents interacting with the rotating media.
 85. The apparatus ofclaim 81, wherein the plurality of cavities correspond to the quantityof rotating media able to be placed in the apparatus.
 86. A method forchanging a head assembly employed in a media writing device, comprising:providing a head mount assembly having a bore passing therethrough;positioning the head assembly adjacent the head mount; aligning the headassembly with the head mount; and press fitting the head assembly to thehead mount.
 87. The method of claim 86, wherein the aligning comprisespassing a first relatively narrow device through the head assembly tofix head assembly position.
 88. The method of claim 87, wherein thealigning further comprises passing a second relatively narrow devicethrough the head assembly and the bore of the head mount to align thehead assembly with the head mount.
 89. The method of claim 86, whereinsaid positioning comprises fixedly mounting the head mount to anassembly tool and locating said head assembly adjacent to the fixedlymounted head mount.
 90. The method of claim 89, wherein the pressfitting comprises compressing the assembly tool, thereby pressing thehead assembly against the fixedly mounted head mount.
 91. The method ofclaim 89, wherein said assembly tool comprises a plurality of sections,and said sections employ a spring to draw said sections together andhold said head assembly and said fixedly mounted head mount.
 92. Amethod for replacing drive heads, comprising: abutting a headmaintenance arrangement to a mounting device, said head maintenancearrangement having an ability to receive a drive head; and press fittingthe head maintenance arrangement to the mounting device free of staking.93. The method of claim 92, further comprising: removing the head fromthe head maintenance arrangement prior to said abutting.
 94. The methodof claim 92, wherein said head maintenance arrangement comprises a headassembly.
 95. The method of claim 92, further comprising providing themounting device with a bore passing therethrough prior to said abutting.96. The method of claim 95, further comprising aligning the headmaintenance arrangement with the mounting device.
 97. The method ofclaim 96, wherein the aligning comprises passing a first relativelynarrow device through the head maintenance device to relatively fix headmaintenance device position.
 98. The method of claim 97, wherein thealigning further comprises passing a second relatively narrow devicethrough the head maintenance device and the bore of the mounting deviceto align the head maintenance device with the mounting device.
 99. Themethod of claim 92, wherein said abutting comprises fixedly mounting themounting device to an assembly tool and locating said head maintenancedevice adjacent to the fixedly mounted mounting device.
 100. The methodof claim 99, wherein the press fitting comprises compressing theassembly tool, thereby pressing the head maintenance device against thefixedly mounted mounting device.
 101. The method of claim 99, whereinsaid assembly tool comprises a plurality of sections, and said sectionsemploy a compression device to draw said sections together and hold saidhead maintenance device and said fixedly mounted mounting device.
 102. Asystem for replacing a drive head in a media writer, comprising: anassembly tool having a plurality of component parts; a clamping devicefor receiving the assembly tool; a drive head maintenance apparatus formaintaining the drive head; and a mount; wherein the assembly tool hasthe ability to hold the drive head maintenance apparatus adjacent themount and the clamping device has the ability to compress the assemblytool, thereby press fitting the drive head maintenance apparatus to themount.
 103. The system of claim 102, further comprising at least onealignment pin for aligning the mount with the drive head maintenanceapparatus in connection with the assembly tool.
 104. The system of claim102, wherein said assembly tool further comprises at least onecompression device for applying pressure between the component parts tomaintain the mount and drive head maintenance apparatus.
 105. The systemof claim 103, wherein said mount comprises a bore, and at least onealignment pin passes through the drive head maintenance apparatus andthe bore in the mount.
 106. A drive head change apparatus, comprising: ahead assembly having the ability to support hardware comprising at leastone drive head; and a head mount tab for adjoining the head assembly topositioning hardware, wherein said head assembly is affixed to said headmount tab in a removable manner thereby minimizing potential damage tosaid mounting tab.
 107. The apparatus of claim 106, further comprisingat least one alignment pin for aligning the head mount tab with the headassembly prior to press fitting the head assembly to the head mount tab.108. The apparatus of claim 107, wherein said head mount tab comprises abore, and at least one alignment pin passes through the head assemblyand the bore in the head mount tab.
 109. The apparatus of claim 106,further comprising an assembly tool for holding the head mount tab. 110.The apparatus of claim 109, wherein the assembly tool has the ability tohold the head assembly adjacent the head mount tab.
 111. The apparatusof claim 110, further comprising a clamping device having the ability tocompress the assembly tool, thereby press fitting the head assembly tothe head mount device.
 112. The apparatus of claim 109, wherein saidassembly tool further comprises at least one compression device forapplying pressure between the component parts to maintain the mount anddrive head maintenance apparatus.
 113. A system for detecting movementof a plurality of disks mounted to a spindle, comprising: atransmitter/receiver capable of emitting a first beam of energy towardsaid spindle and receiving energy from said spindle; and an errorcalculator determining differences between actual head position based onsaid reflective element position and orientation of the spindle. 114.The system of claim 113, wherein said transmitter/receiver comprises aninterferometer, and said energy comprises light energy.
 115. The systemof claim 113, wherein the transmitter/receiver comprises a laser diodeand an optical detector.
 116. The system of claim 113, wherein thespindle is polished to provide a high degree of reflectivity.
 117. Thesystem of claim 113, wherein the spindle is at least partially coveredwith a reflective material.
 118. The system of claim 114, wherein theinterferometer comprises a dual beam interferometer, and thetransmitter/receiver further comprises a plurality of optical detectors.119. The system of claim 113, wherein the spindle has a circumferenceand where the spindle comprises elements regularly spaced around thecircumference of the spindle.
 120. The system of claim 113, furthercomprising a lensing arrangement for receiving light energy andconverting said received light energy into collimated light energy. 121.A system for positioning a head over a disk, said disk mounted to aspindle, comprising: a transmitter/receiver capable of emitting a firstbeam of energy toward said spindle and receiving energy from saidspindle; a reflective element positionally emulating the head andoriented to receive a second beam of light energy from saidtransmitter/receiver and reflect the second beam back toward saidtransmitter/receiver; and an error calculator determining differencesbetween actual head position based on said reflective element positionand orientation of the spindle.
 122. The system of claim 121, whereinsaid transmitter/receiver comprises an interferometer, and said energycomprises light energy.
 123. The system of claim 121, wherein thetransmitter/receiver comprises a laser diode and an optical detector.124. The system of claim 121, wherein the spindle is polished to providea high degree of reflectivity.
 125. The system of claim 121, wherein thespindle is at least partially covered with a reflective material. 126.The system of claim 122, wherein the interferometer comprises a dualbeam interferometer, and the transmitter/receiver further comprises aplurality of optical detectors.
 127. The system of claim 121, whereinthe spindle has a circumference and where the spindle comprises elementsregularly spaced around the circumference of the spindle.
 128. Thesystem of claim 121, further comprising a lensing arrangement forreceiving light energy and converting said received light energy intocollimated light energy.
 129. A method for positioning a head above adisk rotating about a spindle, comprising: transmitting a first lightenergy beam to said spindle and receiving light energy reflected off thespindle; transmitting a second light energy beam to a reflective elementpositioned to substantially emulate head position; receiving lightenergy from said transmitting that is reflected off the reflectedelement; computing an error signal based on positional differencesbetween said spindle, said emulated head, and disk orientation; andaltering head position based on the computed error signal.
 130. Themethod of claim 129, wherein the reflective element comprises a cornercube mounted to an e-block.
 131. The method of claim 129, wherein thefirst light energy transmitting beam and second light energytransmitting beam emanate from a dual beam interferometer.
 132. Themethod of claim 129, wherein the second light energy beam is collimated.133. The method of claim 129, further comprising transmitting a thirdlight energy beam to the disk to provide z-axis measurement and providetilt data.
 134. The method of claim 129, wherein orientation of thefirst light energy beam is approximately 90 degrees different fromorientation of the second light energy beam.
 135. The method of claim129, wherein orientation of the first light energy beam is greater thanapproximately 45 degrees from orientation of the second light energybeam.
 136. A system for accurately positioning a head over a media disk,said media disk rotating about a spindle, comprising: a dual beaminterferometer emitting a first beam of light energy toward said spindleand receiving reflected light energy from said spindle; a reflectiveelement positionally emulating the head and oriented to receive a secondbeam of light energy from said dual beam interferometer and reflect thesecond beam back toward said dual beam interferometer; an errorcalculator determining differences between actual head position based onsaid reflective element position and orientation of said spindle. 137.The system of claim 136, further comprising a lensing arrangement forreceiving light energy transmitted from the dual beam interferometer andconverting said light energy into collimated light energy.
 138. Thesystem of claim 136, wherein the reflective element comprises a cornercube mounted to an e-block.
 139. The system of claim 136, wherein thesecond light energy beam is collimated.
 140. The system of claim 136,further comprising transmitting a third light energy beam toward thespindle to provide z-axis measurement and provide tilt data.
 141. Amethod for efficiently positioning a head above a media disk rotatingabout a spindle, comprising: transmitting a first light energy beam tosaid spindle and receiving light energy reflected off the spindle;transmitting a second light energy beam to a reflective elementpositioned to substantially emulate head position and receiving lightenergy reflected off the reflective element; computing an error signalbased on positional differences between said spindle, said emulatedhead, and disk orientation; and altering head position based on thecomputed error signal.
 142. The method of claim 141, wherein thereflective element comprises a corner cube mounted to an e-block. 143.The method of claim 141, wherein the first light energy transmittingbeam and second light energy transmitting beam emanate from a dual beaminterferometer.
 144. The method of claim 141, wherein the second lightenergy beam is collimated.
 145. The method of claim 141, furthercomprising transmitting a third light energy beam to the disk to providez-axis measurement and provide tilt data.
 146. The method of claim 141,wherein orientation of the first light energy beam is approximately 90degrees different from orientation of the second light energy beam. 147.The method of claim 141, wherein orientation of the first light energybeam is greater than approximately 45 degrees from orientation of thesecond light energy beam.
 148. A system for accurately positioning ahead over rotating media, said rotating media able to spin about acenter axis, comprising: an interferometer having the ability to emitlight energy and measure an effective distance between said head andsaid spindle; and means for computing a correction factor to be appliedto said spindle to correct for any perceived distance errors related tosaid head measurement.
 149. A system for determining spindle orientationinaccuracies, comprising: an interferometer having the ability to emitlight energy and measure an effective distance between saidinterferometer and said spindle; and means for computing a correctionfactor for application to the spindle to correct for perceived errors.150. The system of claim 149, wherein the interferometer comprises a tricoupler.
 151. The system of claim 149, wherein the light energy emittedfrom the interferometer is collimated.
 152. The system of claim 149,further comprising transmitting an additional energy beam toward thespindle to ascertain z-axis performance and tilt data.
 153. The systemof claim 149, wherein orientation of the light energy is approximately90 degrees different from orientation of the additional light energybeam.
 154. The method of claim 149, wherein orientation of the lightenergy is greater than approximately 45 degrees from orientation of theadditional light energy beam.
 155. A method for minimizing media writingerrors in a computing device, comprising: writing a portion of a databurst on a first pass; and writing additional portions of the data burston subsequent passes.
 156. The method of claim 155, wherein the databurst comprises a number of dipulses, and wherein writing the portion ofthe data burst comprises writing one dipulse on the first pass and allremaining dipulses on the second pass.
 157. The method of claim 156,further comprising computing an energy value for multiple bursts writtenusing the multiple passes.
 158. The method of claim 157, furthercomprising evaluating the computed energy value and rewriting theportion and additional portions if the energy value exceeds apredetermined threshold.
 159. A method for increasing magnetic diskyield during the manufacturing process, comprising: initially writing afirst complete set of servo data to a magnetic disk; subsequentlywriting at least one additional set of servo data to the magnetic disk;evaluating the quality of the servo data written; and removing thelowest quality servo data and retaining the highest quality servo data.160. The method of claim 159, wherein said initially writing and saidsubsequently writing comprises writing the first complete set and the atleast one additional set to a substantially identical region on themagnetic disk.
 161. The method of claim 159, wherein the evaluatingcomprises averaging the qualities of servo data written.
 162. The methodof claim 159, further comprising assessing head quality based on saidevaluating.
 163. The method of claim 162, further comprising removingheads of inferior quality indicated by said evaluating and saidassessing.
 164. The method of claim 159, wherein said initially writingcomprises: partitioning the first set of servo data into multipleoverlapping contiguous segments and a first predetermined quantity ofthe overlapping contiguous segments are written during a first pass.165. The method of claim 164, wherein the subsequently writing compriseswriting a second predetermined quantity of the overlapping contiguoussegments to the disk.
 166. The method of claim 159, wherein saidevaluating comprises determining energy perceived by reading the firstcomplete set and the additional set of servo data.
 167. The method ofclaim 166, wherein the energy comprises a difference between the firstcomplete set of servo data and one additional set of servo data dividedby the sum of the first complete set of servo data and the oneadditional set of servo data.
 168. The method of claim 166, whereininitial and subsequent writing is determined unsatisfactory if theenergy exceeds a predetermined threshold.
 169. A method of writing to adisk, comprising: writing data to the disk; rewriting said data to thedisk at locations offset from data previously written to the disk; andremoving data having lowest quality from the disk.
 170. The method ofclaim 169, wherein the data comprises servo data.
 171. The method ofclaim 170, wherein the servo data comprises one set of servo data and atleast one additional set of servo data.
 172. The method of claim 171,wherein said writing and said rewriting comprise writing the firstcomplete set and the at least one additional set to a substantiallyidentical region on the magnetic disk.
 173. The method of claim 170,further comprising evaluating quality of servo data written to the disk.174. The method of claim 173, further comprising assessing head qualitybased on said evaluating.
 175. The method of claim 174, furthercomprising removing heads of inferior quality indicated by saidevaluating and said assessing.
 176. The method of claim 170, whereinsaid writing comprises: partitioning the first set of servo data intomultiple overlapping contiguous segments and a first predeterminedquantity of the overlapping contiguous segments are written during afirst pass.
 177. The method of claim 176, wherein the rewritingcomprises writing a second predetermined quantity of the overlappingcontiguous segments to the disk.
 178. The method of claim 173, whereinsaid evaluating comprises determining energy perceived by reading thefirst complete set and the additional set of servo data.
 179. The methodof claim 178, wherein the energy comprises a difference between thefirst complete set of servo data and one additional set of servo datadata and the one additional set of servo data.
 180. The method of claim178, wherein initial and subsequent writing is determined unsatisfactoryif the energy exceeds a predetermined threshold.
 181. A servo datawriting apparatus, comprising: means for writing data to a disk; meansfor rewriting said data to the disk at locations offset from datapreviously written to the disk; and means for removing data havinglowest quality from the disk.
 182. The apparatus of claim 181, whereinthe data comprises one set of data and at least one additional set ofdata.
 183. The apparatus of claim 182, wherein said writing and saidrewriting comprise writing the first complete set and the at least oneadditional set to a substantially identical region on the disk.
 184. Theapparatus of claim 182, wherein said writing and said rewriting comprisewriting the first complete set and the at least one additional set tosubstantially different regions on the disk.
 185. The apparatus of claim181, further comprising means for evaluating quality of data written tothe disk, said evaluating means providing an evaluation to said removingmeans.
 186. The apparatus of claim 185, wherein said evaluating meansdetermines energy perceived by reading the first complete set and theadditional set of data. divided by the sum of the first complete set ofservo
 187. The apparatus of claim 186, wherein said evaluating meansdetermines writing and rewriting is unsatisfactory if the energy exceedsa predetermined threshold.
 188. A method of assessing track writingperformance on a media, comprising: monitoring spindle axis positionwith respect to a reference position; and providing said spindle axisposition with respect to a reference position to a processor.
 189. Themethod of claim 188, wherein said monitoring comprises evaluatingspindle axis position using a sensing device.
 190. The method of claim189, wherein the sensing device comprises an interferometer.
 191. Themethod of claim 190, wherein the interferometer comprises a differentialinterferometer.
 192. The method of claim 188, wherein said monitoringcomprises evaluating spindle axis position using a capacitance probe.193. The method of claim 188, wherein the monitoring comprisesevaluating spindle axis position using an inductive sensor.
 194. Themethod of claim 188, wherein the monitoring comprises evaluating spindleaxis position using an alternate position optical sensor.
 195. A methodof computing a media track writing performance metric, comprising atleast one from the group including: computing a standard deviation of anobserved track write radius from a desired track write radius anddecomposing the standard deviation into repeatable and nonrepeatablecomponents; computing time dependent servo mark positions; and computingoptically inferred spindle axis positions.
 196. A method of computing aperformance metric for media track writing, comprising: monitoringposition of a rotating component of a holder maintaining said media;computing a topological radius of a surface of said rotating component;and determining a difference between the rotating component position andthe topological radius, wherein said difference equals rotatingcomponent wobble.
 197. The method of claim 196, further comprisingseparating wobble into a repeatable part and a nonrepeatable part. 198.The method of claim 197, wherein the nonrepeatable part comprisesnonharmonic components.
 199. The method of claim 197, wherein therepeatable part comprises harmonics of a rotational rate of saidrotating component.
 200. A method for biasing at least one disk fixedlyattached to a spindle, comprising: applying a biasing lateral force to afirst disk fixedly attached to said spindle thereby tightly interfacingsaid disk with the spindle at one portion of the disk; and applying adifferently oriented biasing lateral force to any second disk fixedlyattached to said spindle.
 201. A method for biasing a disk attached to aspindle, comprising: applying a biasing lateral force to the diskfixedly attached to said spindle thereby tightly interfacing said diskwith the spindle at one portion of the disk.
 202. A system formaintaining media, comprising: a cap; at least one spring holding thecap; and a fluid release ball bearing arrangement having the ability toslidably engage and release said cap using force generated by the atleast one spring.
 203. A device for maintaining media, comprising: afluid release arrangement having the ability to slidably engage andrelease a cover.
 204. A device for holding a rotating hub, comprising: achuck clamp housing; a mounting plate fixedly mounted to the chuck clamphousing; a spindle within the chuck mounting plate; a chuck clampsurrounding the chuck mounting plate and having the ability to engagethe hub, wherein said chuck clamp comprises a plurality of fingerelements.
 205. The device of claim 204, further comprising a Bellevillespring and a fluid release system providing the ability to attach andrelease said device and said hub.